He was noticing how analytical I am and all of that, so in order to clarify, I said that I study rationality and try really really hard to make the best decisions I could, and that rationality helps you do that.

The interesting question is whether the thing that puts people of is nothing how analytical you are (i.e. the evidence of rationality) or whether it's you saying that you try really hard to make the best decisions you can.

Alternatively, this happens less often but if I'm in a "deep-ish" conversation and I'm asked some question of the form "what are you interested in" or "what do you care about" or "what are your goals", I answer truthfully, and to answer truthfully I have to mention rationality and give a brief primer.

If I ask someone "what do you care about" my reaction to the person is likely not directly related to the content but whether the person is passionate in giving the answer.