The people smiling were smiling because they are parents or caretakers themselves and know you can't do much to stop him. You don't need to worry about them; they're entirely in your corner. The people frowning have never spent time with a toddler, so their opinion doesn't count (and shouldn't!). I woudn't worry about them; their day is coming, or maybe never, and either way, their opinions are moot. You're right that ignoring the behavior is the quickest way to stop it, and far more effective than lashing out at him. My son gets into "screeching" phases, and I will usually cover his mouth (gently) with my hand and firmly say, "No screeching!" It takes a couple of repeats, but he'll get it eventually, stop screeching for a day or week, and then pick it up again. Someone once told me that it takes 25 repeats before a toddler will understand what you're telling him/her. (No idea how many more it takes before they comply!) I say don't be ashamed; be proud that you're hanging in there and doing great. Good luck!