As far as can be determined, peppers don't (by themselves) cause ulcers. And may even be a treatment, at least according to [link|http://mn.essortment.com/pepticulcerdis_rzqe.htm|this page].

Cayenne pepper capsules however, are a time honored treatment for ulcers in Europe. Cayenne works at rebuilding damage stomach linings and increases the stomach's production of mucus. Take up to 3, 450-mg. tablets with food and a glass of water daily.

Of course you can "prove" anything with what you find on the web nowdays, but I've seen other sources that say (at least with cayenne peppers) that it does not hurt and may help stomach/intestinal problems.

I would think that if someone has open bleeding ulcers in their intestinal tract, pretty much *anything* (peppers, rice, milk, grass, sand) would be harmful.