Do you mean single-issue voters who say "I'm a Democrat because I am pro-gay marriage, even though I support these mostly GOP or Libertarian policies, but they are not nearly as important to me as equal rights for all genders"?

• No. I mean single-issue voters who say "I'm a Democrat because I am pro-gay marriage." The "Even though" doesn't even need to enter into it.

I have trouble understanding how this is related to the whole discussion. Are you replying to some implicit argument?

• I'm commenting on an implicit fact which may have a bearing on the argument. The loudest members of political groups tend to be those who believe in the political group itself, rather than its specific goals. (Which we should expect; somebody engaging in political signaling isn't likely to do so quietly, as that defeats a large part of the signaling to begin with.)