To be clear any prohibitions on drawing Muhammad are not contained in the Koran, but rather in the Hadith. In simple terms, the Hadith are basically the biography of Muhammad. They were written by many of his contemporaries of the day, and as such we should wonder about the accuracy of some of these. Needless to say you have to wonder about the accuracy of the Koran as well. However, if they are taken as gospel fact by Muslims then they are a valid source to criticize.
So the reason behind drawing the Prophet is a lot more complicated than showing disrespect. Actually I am lying, the reason is far more simpler. It is wrong to draw anything in Islam. Yes, with a completely anti-climatic twist the Hadiths explicitly state that art is bad and if you are an artists you will go to hell. Of course you don't have to take my word for it, so here are the Hadiths explaining a simple answer that I could not get from my opponent. The answer to this question was eventually found on Quora, so it was searching for the answer that lead me to the insane conclusion.
Sahih Muslim 2109 b
"Verily, the most grievously tormented people amongst the denizens of Hell on the Day of Resurrection would be the painters of pictures.
Sahih al-Bukhari 7557
Allah's Messenger said, "The painter of these pictures will be punished on the Day of Resurrection, and it will be said to them, Make alive what you have created.' "
Sahih al-Bukhari 3224
"Don't you know that angels do not enter a house wherein there are pictures; and whoever makes a picture will be punished on the Day of Resurrection and will be asked to give life to (what he has created)?"
There you have it Islam is void of any great art and artists according to themselves. Even if some great artists said they were a Muslim, the simple truth is that they are not as they will go to hell. Sorry Cat Stevens aka Yusuf Islam you are going to hell, luckily its not true.
In closing, I disagree with this as there are beautiful depictions in Islam art as well as architecture. However, according to Islam they are ugly as art is forbidden.
Funny religion, go get the straight jackets.