The overriding unity of Islam is the overwhelming desire to have sharia as the global unifying principle. This is unequivocal in Islamic belief. Anyone who takes seriously the Koran, and most Islamics do, believe that either by demographics or by Jihad this will take place. The muted responses by most Islamics when 9/11 happened and subsequently their behaviour, particularly from the seat of Islam - Saudi Arabia - display the simple fact that Islam is a dangerous virus which has its viral infections spread over most of this world but particularly in the free world. Call it Islamism if you will. Even Pipes states that Islamists make up 10-15% of the global Islamic population. If you think that 150,000,000 adherents does not present as a global danger than you are very naive. This, in addition to the fact that the sharia ideology is a mainstream ideology in Islam regarldless of the ultimate means envisaged to accomplish that end.
I know from personal experience that most Muslims really do just want to live their lives and get by. There are exceptions, and these need to be dealt with - resolutely and harshly - but you can't tar all Muslims everywhere with the brush of the global jihad.
This is the tactic which has been used by Islamic sympathizers. They attack people who point out the pervasive problem of Islam by resorting to the "guy down the street" nonsense. Keep the little-town Islamic rhetoric to a minimum it only points out that you're more inclined to be the next victim of the quiet Islamic down the street...or rather your neighbour who you've lulled into believing your home-spun Islamic myths.
What happened on 911 was, by the standards of the Noble Qu'ran, harram. Of course, you have Muslims out there who don't see it that way, just as you have "Christians" who think it's okay to act like animals. They all can be found, f**ked and forgotten, and I'll shed no tears for any. But I won't accept that all are bad because of the actions of the mad, the bad and the thankfully few.
Here again you bring christians into your relativized rhetoric. Your perceptions are unfortunately reflective of many Islamics who try to whitewash the global menace by pointing out disparate nut-cases in other religions. It wont work with this poster.