I believe in A, I don't take a strong position on B, I am in coalition with people who believe in B and don't take a strong position on A, we both believe in C, D, E, and F, which some other people believe in with differing weights. Browbeating me about position B (or, the most useless kind of Internet banter, complaining about me and my hypocritical position on A+B to your friends who oppose both in a likewise contradictory way, in some venue I've never heard of) is not about making people reevaluate positions, it's about negative factionalism. The only reason it might not fit the familiar categorization of "fallacy" is that you would never use it in rational debate, either in arguing with another person or in reasoning out your own position.