Here's the thing that you're forgetting: the targets of (e.g.) hateful rhetoric feel better when bigots are dismissed from polite society. Some bigots may become more radicalized, but many become demoralized or may even think twice about it (see above). However, when fewer people are allowed to propagate bigoted views in society, society overall is a better place. The whole point is to make society more inclusive. I care less about marginalizing people with abhorrent views than marginalizing different ethnicities, lifestyle choices, and genetic predispositions.
"Wait until they die" suggests a bootstrapping problem: why would children of bigots feel any different unless they had a reason to? If you only wait for bigots to die out instead of marginalizing them, bigotry is normalized over generations. You have to interrupt that cycle.
I'm of the opinion that these kind of tactics probably aren't as effective as simply what I suggest: "letting the old people die". It's been shown that young people hugely disproportionatly support gay marriage, and support for Prop 8 is declining by a large percentage every year.
I think that when you decide that certain viewpoints or groups are just not allowable at all, all you do is marginalize those groups and push them even further to the extreme. I think you could make a case that Fox News et al would possibly be less extreme if the progressive movement wasn't so vocal about eradicating all potential opposition.
Just my two cents. I'd be really interested to hear other's thoughts on this subject, because I think that bigotry is tied to a whole bunch of other related problems that need solving.