It's the cross you bear.
"Shawn... YOU of all people will appreciate THIS" (insert shitty tattoo photo here).
It happens with strangers too.
"When I get older, I'm going to look like YOU" (I always retort "What, a dorky manchild?")
"I haven't gotten it YET, but (insert long drawn out story of a tattoo I don't care about).."
"My cousin has this amazing tattoo that (insert tattoo that I don't care about)..."
You just smile.
If they SHOW you a tattoo, respond "yeah, that's a tattoo alright".
if they ask your feedback, respond "yeah, that could totally work".
That or do what I did at the bar the other night:
"honestly, I could care less. So. you want a drink?"