Here's a question for my loyal readers: Is there any position you can think of that you support but that, if you hear someone else supports it, you become more suspicious of them politically?
Perhaps intuitively that makes no sense. If you back a given stance, why would you look sideways at someone else who shares your view? But there are circumstances where I imagine it could make sense -- for example, when you have cause to believe most other people who hold your view do so for bad reasons, are using it as a stepping stone to enable policies you don't support, or that the view most commonly is a valid proxy for other positions one strongly opposes.
Imagine, for example, an African-American opponent of affirmative action, who believes that such programs engender White resentment while doing little to help the most disadvantaged in the Black community. Such a person might nonetheless conclude that most White opponents of affirmative action come to their opposition for other, less tasteful motivations, and so view them with political suspicion. If the person is generally liberal otherwise, they might recognize that most affirmative action opponents are politically conservative and that persons who loudly trumpet their opposition to affirmative action often are especially conservative (and even more especially-so on racial issues). Any of these could give cause to view your putative compatriots a bit askance.
One can imagine other circumstances as well. Someone who supports a ban on assault weapons but not a total prohibition on the sale of handguns might believe that many people who back the former do so in order to make the latter more palatable or feasible -- essentially a slippery slope argument. Where one has multi-peaked preferences (e.g., one prefers only an assault weapons ban > no gun ban > complete gun ban), then one might not want to empower who share your support for an assault weapons ban on the theory that they, unlike you, want to go much further than that (see this article by Eugene Volokh for more on how these mechanisms work).
So I'll pitch the question again: Can you think of any policy areas where this applies to you? Positions that you hold, but where you're suspicious of most other people who claim to hold them? It's an interesting question, I think.