Got into a conversation with a friend about things we do completely innocent in motive but then in hindsight feel like douche bags for doing. Kinda interested to see if this is a more shared experience, since this is coming from a guy who usually could care less and is pretty blunt.
An example today:
On break from school for now and my parents seem compelled every now and then to buy me clothes. Usually ones I'd not really wear outside of the house just because they "aren't me". My dad comes in with a shirt that's this really weird green color with strange stitching and I just offhand said what I thought about it without thinking much, like always, and he had this injured puppy look in his eyes. Knowing him if it did bother him he was fine 10 minutes later but I totally felt like a little shit for it.
I was dumped and experienced another huge betrayal. It's been 3-4 months and I still can't sleep regularly because I feel like it's my fault. Also, I suddenly want to apologize to everyone even though I'm quite aware that I've done nothing to apologize about..
By the way OP, in your case I think it's only natural to feel like a jerk when someone brings something you despise. Probably because he brought you it because he thought you would like it, or because he liked it and wanted you to have it. You might have felt like you stepped on his taste. If that makes any sense at all. Anyway, being honest is likely what hurts the least. Considering someone keeps mentally hurting themselves when they never see you wearing what they brought you.