We've got to think in terms of "What would a blind multiculturalist think about this?" How would they see it? How do they hear you? We've got to reach them. They are looking for a reason to discount this.
What can we do to become more effective? My first suggestion may sound elementary, but it's important: Spell correctly. If you write anything anywhere, double- and triple-check your writing. Make it as free of mistakes as you can, as professional as you can, and as articulate as you can. Avoid emotional rambling. Make your point as succinctly as you can with as much logic, reason, and evidence as you can.
Same goes for what to do when you're speaking to someone in person too. Give them no easy reason to dismiss what you're saying. Go out of your way to avoid hitting their triggers. Don't throw in conspiracy theories in the middle of your comments. Don't go off on tangents about anything a multiculturalist would consider "right wing," like gun laws or stockpiling weapons and ammunition.
You've got to get inside their heads and imagine looking over at you through their eyes, with their point of view. You have legitimate information and, if they understood it, they would change their mind, and might even want to do something about it.
And don't come off as if you know something and they are ignorant, even if it's true. Don't come off as better than others. We are not better than others because we know about Islam and they don't. It doesn't make us superior — it burdens us with a responsibility that we had better take seriously: The responsibility to get through to our fellow citizens and help them understand something they wish wasn't true.
Being right isn't good enough. Plenty of people in history were right and failed. Those who opposed the Communist revolutions in Russia, China, and Cambodia were right — and they lost. We have to be effective, not just right. You will make no converts being an obnoxious know-it-all. I've tried it. ;-)
Think back to before your eyes were opened. If someone came at you wild-eyed and full of seemingly-racist conspiracy theories, you would probably have recoiled from it, and recoiled from the point of view, and recoiled from the idea that Islam might be dangerously different from other ideologies you're familiar with, and you may never have given that idea any serious thought again.
We need to be careful. We cannot afford to lose people like that. We need to present our information as a realistic, unexaggerated, well-grounded, authoritative understanding of world. We need to make it clear that important people "in the know" also see it this way. We need to avoid presenting it as something "nobody else knows," because they will think, "Yeah, right. You have figured out what the mucky-mucks in the Pentagon haven't figured out? Sure, buddy. Why don't you calm down and we'll give you a sedative."
We need to be perceived as reasonable. We need to have our facts straight and well-memorized. We need to be persuasive. We must win people over to our side, and we must do it as quickly as possible.