Does Amplification create the talking and the lack of manners by the audience?

I don't think so, at least not at lower levels. Going back to Llandudno in the 80s, in the summer a large part of the audience were holiday makers so I saw quite different groups of people each week. Some weeks were quieter than others and once in a while you would get a noisy table - it was just the way it went.

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I wound up with I think the worst group we had on one of the odd weeks I was doing the MC. This group of 4 were sat closet to the stage and making life difficult/unpleasant for everyone. I tried going over and talking to them but it didn't make a difference for long.

Anyway, I probably shouldn't have done it but I then addressed them over the PA, noting that I'd already spoken to them politely, they were ruining the night for others and that if they wanted to chat there was the main bar. I then told them they had a choice, either enjoy the music quietly or chat in the other room but if they continued to be noisy in the club, I would fetch the landlord who would remove them from the room (and he would have supported this), but I didn't want to andf there was no need for this.

To my amazement, when I finished my "speech", there was loud applause from everyone else in the room. The group got up and stormed out (well one shouted some abuse at me) and in the end, that particular night turned out to be a really good one.