Disclaimer: This is not a perfect comparison but it is a workable one. It's traditional at this point to say something like: “I'm not a racist for talking about Islamic terrorism” but I doubt that will hold any weight for anyone wanting to call me a racist for talking about Islamic terrorism.
The American Gun Control problem can be phrased simply as: “Is the gun owner a good gun owner or a bad gun owner?” The bad gun owner is the angry teenage boy who will go into a school and shoot people. The good gun owner is the woman wanting to make sure she can defend herself, if assaulted. The difficultly is twofold: a) determining which is which at point of purchase and b) determining which is which within the gun owning community (36% of US population).
The Islamic terrorism problem can be phrased similarly: “Is the Muslim a good one or a bad one?” The bad ones are the angry men who will drive cars into people and blow up pop concerts. The good ones are happy to co-exist with Westerners. The difficult here is also twofold: a) determining which is which at point of entry into the country and b) determining which is which within the current Muslim community (4.5% of UK population).
In both cases, a minority of each community are violent killers who will show no regard for the sanctity of human life. The very existence of this minority brings the whole community into disrepute.