Yes they did get it wrong, but then they don't give a hoot about anything other than selling papers by using flashy headlines and stirring the ordure.
I'm fairly sure that Muslims do discuss and debate issues like ISIS and other such groups, but they do it within the family, the community and the mosque, all of which takes time before a consensus is reached.
And before someone decides to jump on me for that statement, I will just point out that Islam is fundamental to the daily life of Muslims, and that while individual members of that faith may well abhor the actions of ISIS and other extremist groups, the debate within the community is about the interpretation of Islam being used by those groups to justify their actions, hence the time taken to condemn them as a community.
As regards the Sun's sign to put in your window - anyone who is Muslim and does so will make themselves a target for all the idiots who believe all the anti-Muslim headlines they see in the papers and first few paragraphs of the accompanying articles. The Imam of the mosque in Southfields (the oldest mosque in London) has been targeted by local idiots - bricks thrown through windows, racist graffiti daubed on the walls of his house and the like.
As far as I know, that mosque, and others I know of in the area, have never been associated with extremist views or fundamentalist Islam, not that that makes a blind bit of difference to the believers of the headlines of some tabloid newspapers.