Hi (or hey) is often, if not usually, followed by "How are you?" and/or "It's good to see you". If I were greeted with a grunt or "yo", it would be a surprise as it's not the cultural norm here. I'm not sure I'd know they were addressing me, but if I did, would try to model better behavior by answering with "Hi" or "Hello".
When people are grousing about electric cars, I often thing along the lines of what Stitchnripper has mentioned. When combustible engines came out, they were not perfect, and many didn't think they would ever replace horses, distrusted them, etc. - yet here we are. It turns out that wind turbines aren't the greatest green energy source - but they were an idea, a beginning of looking at possibilities and options. It is, as the saying goes, progress.