Problem 1: They either play it off because they did not take the time out to research the utility or do not understand the concept. (solves double spending etc).
Bitcoin doesn't solve double spending. In fact, it's the only thing that can be double spent, and is a large part of the need for grossly inefficient mining. Some things that it does "solve" are charge backs and counterfeiting.
Explain that one. The part about inefficient mining. While you are at it, suggest a better alternative. Something more than "PoS" (at least elaborate if that is your answer).
Hey, I don't know a better alternative (PoS is exactly that, a Piece of Shit) but you you can't tell me that mining is an efficient use of resources. I don't know the exact numbers these days, but I know in 2011 it was something like $45k/hour in electricity costs, and has only gone up since. I realize that on a Gh/s/KwH basis, mining has gotten more efficient, but it's far from ideal. So sit down, shut up and take your Ritalin, because I wasn't attacking your precious Bitcoin.