1) Don't really have to. I smoke in my own domicile and everyone around me adjusts. Primarily get compliments about the smoke's aromas. Only once did I get a sheepish comment about a Perfecto Garcia brand being smoked and that it was the one cigar they smelled that actually stunk!
2) If it was a case of back-to-back banter, all one has to do is point out how active and regular cigar smokers Milton Berle, George Burns (who smoked 20 CHEAP cigars everyday), Zino Davidoff, and endless other names survived into their late '80's, early '90's, and even 100 years of age!
Point out to them something Redd Foxx once said, "People don't drink. Don't smoke. Don't eat pork. No biscuits, no gravy with onions in it...because they wanna live - you're gonna feel like a damn fool laying in the hospital dyin' from NOTHIN'!"