Sorry but if it's comming right out or right near your a-hole then it's not likely your average skin tag, it's more than like perianal crohn's disease and if your GI says it's not then I'd be getting a second opinion on that TRUST ME, I was told mine were just hemmies and developed some serious issues with them and ended up have an emergency hemheroidectomy done on them only to find out shortly after that it was infact perianal crohn's skin tags...and you don't want to mess with them (and they're only related to crohn's disease NOT UC).
check out this link....if itn looks anything close to the pic BELOW the pics of hemmies then that's what you have...
http://www.emedmag.com/html/pre/fea/features/011504.asp