Haha yeah you're gonna get the DEA at your door for warning someone about drugs, Einstein. Your post is incriminating enough anyway because you must be off your face to think any police would set up such a weird and specific sting operation, Mr Paranoid.
Anyway I've got UC and I know for a fact that taking LSD with UC might (probably definitely will) give you some flare-up symptoms for at least the duration of the trip. Sitting on the dunny for half your trip or curled up with cramps is not a great way to get enlightened and become one with the universe. Shrooms play havoc with your guts even in healthy people so it's even worse. I've done both though, very irregularly, and LSD is far less likely to cause you (well, me) more dramas than Shrooms. Probably goes without saying since theyre hard on everyone's guts.
That said, using your judgement, depending on the severity of your symptoms at the time you could likely get away with it once in a while if your remissions are reliable. Obviously don't take it while you're flaring, nothing good can come of that. I can only speak in personal anecdotal evidence but can confirm for me there was no interaction between any of the meds I was on (Prednisone, mesalazine, mercaptopurine) just a few trips to the shitter that I probably wouldn't have needed if I didn't take it. I had minor flare symptoms for about the duration of the trip (read: avoid tripping at festivals etc unless you love port-a-potties). I would sometimes maybe keep flaring the day after too but nothing major. So basically LSD is probably about as bad as a burrito.
Responsible question though and I know it's a pretty vague answer, at the end of the day you've gotta decide how much UC is gonna run your life. Some people stop drinking coffee when they get diagnosed, I'd rather just get a colostomy bag if I had to give that up.
I don't know about any potential dangerous interactions (I'll volunteer for that study if they ever do it. More than happy to wig out in the name of science) but I doubt there's much real data other than from backyard scientists quoting Wikipedia or from anecdotal stories like mine, so if OP is gone I'm sure this might help someone in the future anyway.
While we're on the subject, the constipating effects of opiates did wonders for my bowels. Obviously not a long term solution but if opiates were anyone's DOC they can rest assured because mine were prescribed by a doctor who knew I had UC. Not saying take oxy instead of acid, just sharing my experiences.
You mentioned coke, I've got nearly 0 experience with that but I do know certain other strong stimulants are awful to take with UC. I'm Australian so meth and dexamphetamine are pretty common here and they rape your guts (not to mention the rest of your body) so you'll be shitting like a goose if you do them, I think adderall are basically dexies aren't they? Keep away I say.
Also, this could just be coincidence but my symptoms seem to lessen when I'm on benzos (by themselves with no other drugs I mean, not like on a comedown off something else), so my theory is that the pre-trip anxiety after dosing LSD but before it hits you may play as much or more of a role in the flare symptoms I described than the LSD itself. And I think it's pretty well known stress isn't good for IBD so that would make sense I guess.
Anyway I've done ketamine on all the same meds too no dramas. MDMA I think is the one to watch out for, I'd do a thorough search online before considering buying or taking any pingers. I have done it myself admittedly but with similar results to the other stimulants, plus I've never really liked it anyway so I don't do it enough to give you much information about it. Hope this helps.
Oh and PS weed is great for those nasty cramps when you're flaring, brings back the appetite the other meds (and the disease) take away.