Muhammad was the creator of Islam.

Sunni Muslims believe he should never be shown to avoid idolising an image of him, which would mean it was about his image and not what he means to Islam.

Though other variations of Islam do allow pictures of Muhammad, the most well-known view is that he should never be displayed in any way.

Extremists generally take people ignoring this rule as desecration of the creator of their beliefs and their religion as a whole, and in rare cases give death threats to those who do display muhammad. though that is rarer than people think.