Recently in Yemen a suicide bomber attacked a ceremony of Shia Muslims celebrating the birthday of Prophet Muhammad:
http://www.bbc.com/news/world-middle-east-30644624

Killing Shias is nothing that radical Sunnis would apologize for and since Shias, contrary to Jews and Christians, have no lobby there will hardly be any outcry or otherwise public condemnation even though the Houthi Shias in Yemen are fighting against Al Qaeda.

What is, however, much more frightening is that instead of condemning the crime or at least keeping silent some Sunni authorities consider the celebration of the Prophets birthday unislamic and forbidden (haram). By arguing in this direction such people at least indirectly „explain“ and justify the attack on the ceremony and side with the perpetrator.

Many islamic websites go at lengths to explain that celebrating the Prophets birthday is not part of the Quran and the Sunnah. Others say it is an innovation (bid´ah) and thus forbidden. Let´s take on these claims one by one:

1. With regards to the Quran one could also say that the exact text of the daily prayers (Salat), it´s times and other detailed aspects are also not part of the Quran. One could confront the extremists with this question: Has the Quran prohibited celebrating birthdays?

2. Declaring something forbidden because it is not part of the Sunnah is a weak argument as the same applies for drugs (Heroin…) as well as medicine (vaccination..). Same with regards to sports or technological innovations. None of this is reported in the Sunnah as being practiced by the Prophet or clearly regulated. Going by this irrationality one could also argue that grapefruits or kiwis are „unislamic“ because the Prophet is not reported to have eaten them. Fact is, anyway, that there is no Hadith where the Prophet explicitly forbade celebrating birthdays.
That the Prophet did not do somethings does not mean that they are unislamic and thus forbidden. For instance, did the Prophet go to school? Did he swim? Did he learn foreign languages?

3. Trying to construct a prohibition for celebrating the Prophets birthday by calling it „forbidden innovation“ (bid´ah) is completely flawed. Celebrating the Prophets birthday is not tantamount to introducing a religious ruling or law. What IS haram is to forbid something which God has allowed or to allow something that God has forbidden. None of this applies to the act of celebrating the Prophets birthday, so the true „innovators“ are those who go as far as to declare such a celebration forbidden.
Declaring such a ceremonial act „innovation“ is as much nonsense as saying that wearing a Lionel Messi jersey while praying or breaking the Ramadhan fasting with rump steak constitutes (unislamic) „innovation“.

What evil can possibly be in Muslims coming together to share food and pray with eachother? What is unislamic in commemorating the Prophet on his birthday and speaking prayers and poems to his remembrance?
Does not the Quran say: „God and His angels send blessings on the Prophet: O ye that believe! Send ye blessings on him, and salute him with all respect.“ (33:56)?

Although the following verse refers to allowed and forbidden food it still gives guidance regarding how to deal with „do´s and dont´s“:
„But say not – for any false thing that your tongues may put forth,- „This is lawful, and this is forbidden,“ so as to ascribe false things to God. For those who ascribe false things to God, will never prosper. “ (16:116)

„What think those who invent lies against ALLAH of the Day of Resurrection ? Surely, ALLAH is Gracious towards mankind, but most of them are not thankful.“ (10:60)

„My Lord has only prohibited indecencies, those of them that are apparent as well as those that are concealed, and sin and rebellion without justice, and that you associate with Allah that for which He has not sent down any authority, and that you say against Allah what you do not know. “ (7:33)

It is by no means obvious in how far the verse above could contain the celebration of birthdays as part of the „catalogue of prohibitions“. At the same time a pious Muslim has no reason to assume that Allah has „forgotten“ anything as the Quran clearly says:

„…WE have left out nothing in the Book…“ (6:38)
„Shall I seek other than Allah for judge, when He it is Who hath revealed unto you (this) Scripture, fully explained ? …“ (6:114)
„And the word of thy Lord has been fulfilled in truth and justice. None can change HIS words…“ (6:115)

Extremists argue that music and singing are prohibited in Islam, but again this is untrue. With no word does the Quran prohibit music. This is what it says:
„And assuredly We gave David grace from Us, (saying): O ye hills and birds, echo his psalms of praise! “ (34:10)
This refers to Prophet David singing his Psalms in praise of God, while the hills echoed the melody and the birds accompanied it with harmonic twitter.

While there are very few Sahih Hadiths that seem to indicate that music instruments are forbidden in Islam, there are at least three Sahih Hadith that indicate the opposite:

„That the Prophet said to him‘ „O Abu Musa! You have been given one of the musical wind-instruments of the family of David .‘ “ (Bukhari, Vol. 6, No. 568)

„The Prophet (ﷺ) came to me after consuming his marriage with me and sat down on my bed as you (the sub-narrator) are sitting now, and small girls were beating the tambourine and singing in lamentation of my father who had been killed on the day of the battle of Badr. Then one of the girls said, „There is a Prophet amongst us who knows what will happen tomorrow.“ The Prophet (ﷺ) said (to her),“ Do not say this, but go on saying what you have spoken before.““ (Bukhari, Vol. 5, No. 4001)

„On the days of Mina, (11th, 12th, and 13th of Dhul-Hijjah) Abu Bakr came to her while two young girls were beating the tambourine and the Prophet (ﷺ) was lying covered with his clothes. Abu Bakr scolded them and the Prophet (ﷺ) uncovered his face and said to Abu Bakr, „Leave them, for these days are the days of `Id and the days of Mina.“ `Aisha further said, „Once the Prophet (ﷺ) was screening me and I was watching the display of black slaves in the Mosque and (`Umar) scolded them. The Prophet (ﷺ) said, ‚Leave them. O Bani Arfida! (carry on), you are safe (protected)“ (Bukhari, Vol. 2, No. 987)

Another popular „argument“ of Salafis is that celebrating the Prophets birthday means copying Christians and again that copying Non-Muslims means being one of them. But then what about using AK-47s, firing RPGs or building IEDs? Are these not all acts of „copying Non-Muslims“?

The biggest danger to Islam today is the rise of Wahhabism and Salafism, two extremist „sub-ideologies“ whose supporters consider themselves superior to anyone (including Muslims). They engage in an „exclusivist-narcissistic“ self-perception that takes on fascistoid dimensions climaxing in takfirism, the act of declaring other Muslims „unbelievers“ or „apostates“ (murtadd).
The result is that these people go as far as either directly committing violence against their opponents (including unarmed civilians of all ages and sexes) or they consider violence against their mentioned adversaries at least as lawful (halal).