I am guessing our ancestors had to eat a lot of burnt meat, try cooking at a campfire! Not that is a scientific response :-)
I read this today and was about to post it. I'm all for grilling, personally. Not severely burning things, but a nice char is amazing on a steak.
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I don't think it's a big issue. The small benefit one would get from raw or sous vide all the time is perhaps worth it for a very sensitive person but not for everyone. And I think the main issue with grilling/barbecuing will be the open flame and the marinade (that has of vegetable oils and sugar) getting burned in the process.
These issues in general always seem to be largely irrelevant, the added risk is just so small it's not worth the attention.