Not just a date but I have lost two long-term partners due to Crohns because they couldn't handle it. The first was a woman I had been with for ten years during the time I was diagnosed, and the second partner I was with for three years before she decided the load was too heavy to bear. Unfortunately I don't think this is an uncommon experience for people -- gay or straight -- with chronic illnesses. Frankly, if I could walk away from this disease, I might do the same.
It's hard to know when to divulge to a new person you are seeing. While I think it's important to be up front early on, you also don't want Crohns to define who you are to another person, even if it dictates so much of what you do on a daily basis. I find it works best to be matter-of-fact, not overly dramatic, e.g. Oh, yeah, I inject this stuff, and No, I can't eat that, and Sorry, I've gotta go (and it's not going to be pretty!) Humor helps, too, if you can muster it.
As a lesbian, I've faced some challenges finding a partner who doesn't want to "fix" me. I've been told that if I'd just go on a macrobiotic diet, that if I turned vegan, that if I'd avoid exhaust fumes, etc. the Crohns would go away. I even dated one woman who insisted I didn't have Crohns at all but had celiac disease. (Thank you, Dr. Rainbowomon!)
I believe there are a lot of people out there who can't handle being with someone who has a long-term illness with no cure. You don't want to be with them because you'll either end up lying about symptoms or how you are feeling to protect them, or they will make it all about them, as if they are the one bearing a huge burden. Having Crohns is exhausting enough; you don't need added grief from a partner who can't handle it.
Happily I have been with the same partner now for nearly 12 years and we've been through enough together that I know she's in it for the long haul..