I have no clue about why some people get so upset by self-voting.

My feelings about it are that is an extremely rational thing to do in the short run but may well be somewhat counter-productive in the long-run simply because it somewhat reduces opportunities for engagement in that if you use all of your Steem Power voting for yourself, you can't be using it to vote for others.

But some self-voting may be an optimal strategy.

Meh. As far as I'm concerned people can use their voting power however they choose. Life is too short to worry about whether or not @somerandomdude gave himself a thumbs up.