One of the central elements of the paradigms of Muslims is that Islam is perfect and, thus, may not be critiqued.
Infidels may not critique Islam for a number of reasons. One is that because they are non-Muslims, they cannot possibly understand Islam or even various aspects of it with which they might not agree. Furthermore, as non-Muslims, they do not understand the sacrosanct nature of Islam, being revealed as it is by Allah. Infidels have no understanding or impulse to reverence, it is believed. Besides, only Muslims can understand Islam, so infidels should not stick their noses in areas they do not belong. Any critique of Islam by infidels is irrelevant if not dangerous in that Muslims may be led astray.
Of course, it goes without saying that Muslims believe that as the religion revealed by Allah, Islam is above criticism or critique.
Another element is that issues that are internal to the Muslim world are the business of the Muslim world only. Infidels have no business whatsoever concerning themselves about such internal issues. One reason is because as outsiders, infidels cannot possibly understand the dynamics and conditions of the issue, nor would they be able to understand the various perspectives and the intricate details of the relations among various perspectives and groups. Another reason is that Muslims have been revealed the truth, which infidels by definition do not, and so they possibly cannot apply the rules and standards and dictates of truth to the issue, and so their opinions are irrelevant. A third reason is that infidels have a desire to impose on the Muslims their ideas, ideologies, structures, values, and so on: this is wrong for it has been revealed to Muslims what they should do (and in some cases why, but the wherefores are irrelevant: what matters is what they are to do has been revealed) and thus Muslims are forbidden to borrow from infidels or, for that matter, listen to their advice.
The opposite does not hold true: that is, Muslims believe they are obliged to concern themselves with all matters in the world, even if it is an internal matter of another people. The reason is that Muslims have been empowered with Allah’s revelation and would be the best people to interpret any situation. And since Islam is the true and sole solution to any problem or issue, the involvement of Muslims is crucial to truly solve a problem. Indeed, because the laws revealed by Allah are for all humans, perhaps by being involved they can persuade people to obey Allah by suggesting what Allah has commanded.
All of this exists because of the belief that Islam is real and is the truth (or can explain the truth). As such, it cannot be critiqued because that would not accomplish anything. Criticizing the sun will not affect its rising and setting. Furthermore, any critique of the truth, as they believe it to be, would be an exercise of falsehood.
I write this to explain the mindset of Muslims when it comes to infidels commenting on Islam, and why Muslims do not appreciate the advice or input of infidels