Peace
Quran & Sunnah
Do you think that even Muslims, with even the best intention, also make mistake what's Islamic and what's not Islamic?
Yes, they can make mistakes if they don't have enough knowledge about Islam.
We non-Muslims based on what Muslims say or do, and may not understand what is or is not Islamic, but it would seem that even pious Muslims also mistakes too, which is worse, really.... The reason what I am getting at, being that Muslims also have the tendency to either misunderstand, and hence mis-represent Islam, in some cases, in the worse possible light. Muslims can be Islam's worse enemy.
Yes they can misrepresent Islam if they are not knowledeagble about their religion. They can misrepresent Islam if they cannot distinguish between what is Islamic and what is cultural.
They can misrepresent Islam if they take verses, as some non-muslims do, out of their context and say this is Islam.
You can find a Muslim man bearded and praying the 5 daily prayers at their appointed time and fasts ect... but not having the moral of behavior vis-à-vis others and that's due to his ignorance of Islam. If he is knowledgeable enough he can know that Islam is a religon of good behavior as well, it is a religion of etiquette and that morals and good treatment is part of worship and part of our religion. If he is doing one thing and neglecting the other then his Islam and faith is incomplet.