Is this a bad thing to do?

I don't think you did anything wrong because you were just phrasing it that way as a bargaining chip to get the name of a person who was borderline stalking you at the time. If anything, your boyfriend is the one in the wrong here for sneaking around like this in the first place, especially if he said things like that to you after. Just explain to him that you were just trying to get the person to admit their name and that you wouldn't have kept leading them on in any way.