Manal, wife of Abu Sinan has recently started a blog, and very entertaining it is too. Except she has already had a troll who accused her of "not sounding like a Muslim", which is a nasty and completely unfounded slur.
There is no justification for such behaviour, but the cause of it is simple, yet decidedly unIslamic. We all want to be good Muslims, we want this more than anything else. For some this desire gets mixed up with the longing for others to see what a good Muslim you are, such longings then lead to the childish tactic of calling others bad Muslims so that you look like a good Muslim in comparison.
Or, to put it another way, putting someone else down to make you feel good. Which is less about Islam and more about pride and ego.
We can all be tempted by such thoughts, but there is a simple cure. When you see a Muslim doing something you see as sinful, first consider: "Would I exchange all the sins I currently commit for the sin I feel this person is committing?". Usually the answer is "yes".
Or as Abu Hanifa (RA) so eloquently put it "Oh my eyes, but others have eyes too."