This is a very important point. If for instance yuo are in search for a religion the worst thing you could do is to study the people who follow that religion and not the religion it self. In the world today many muslims make mistakes. Some of these mistakes are harmful to the universality of humanity. Does this mean that Islam is the one which is like this? Not at all. Please study Islam and not the muslims before you make the decision. Salaam and May Allah protect us all. Ameen.
Yes, very true and this further leads to the fact that muslims should study Islam and attempt to become example for those who look at muslims to look at Islam.
When an ordinary person evaluates a religion, his way of doing so will be through those people he knows who practise it. Unless he is really interested or a scholar, he will not want or even maybe able to study it.
So, as an ordinary person, if I want to be able to say something about Islam, I will look to those who profess the religion, who tell me they know about it and practise it. Just as I would do about any other religion. Tell me how many muslims make up their minds about christianity or judaism or hinduism after having studied those religions? They limit themselves to a predigested version full of prejudices and half truths unless they are particularly enlightened people. Just the way non-muslims do when talking about Islam.
So the fact remains that muslims are the true advertising banners of Islam. If they behave badly then - right or not - they will give a bad impression. And if they behave well then the impression is good. Unfortunately the bad impressions made by anyone are much stronger than the good ones... that's the reality.