There are relatively few things I think people should be legally barred from. Let's see...

Murder, assault, theft, property destruction, other wanton acts of violence, pre-emptive war, wanton ecological destruction (uh-oh...), fraud, false advertising (oops! There goes a whole bunch of ads), lying in court or while in public office (yikes! there go most of our politicians), certain diving infractions or other reckless use of equipment in a public area, certain public acts of what would be termed "gross indecency" (this is a tricky area, partially dependent upon social customs...figure it out for yourself), knowingly selling harmful substances to people (arrgh! there goes a whole big piece of the food industry, plus the tobacco industry, and so on), medical quackery (there goes half of the normal activities of the AMA!)....and...um...

Hmmm. It is a complicated subject, isn't it? Nothing in there about gays, though.