1.) There is nothing wrong about gemming and everybody can choose his own playing style.
I Play the game for the fun of progressing and working for my Upgrades. Gemming my whole base to max would reduce the time I can enjoy playing the game, so why should I pay for that?
On the other Hand I also buy gems for boosting, because then I can Play more in the same time, which increases the fun of the game. Until I reached th9 I did not buy any gems, because earning them to get the builders huts was part of the Progress for me. Now it is only boosting or geming single troops if clan war Ends soon and somebody Needs troops quickly and there is not much Progress in getting gems for that.
I dont gem ressources or boost mines (except for 1 gem Events) or gem Upgrades time because builder Management is part of the game for me. It is not so much about costs, even if 100$ per month is a bit too much for a mobile game, but simply to get most fun out of the game.
2.) Most Players are against gemmers because they compensate lack of skill (or lack of raiding experience) with money. You spend money to have a Player Profile that you did not earn. Also most gemmed bases are really bad, because with gems you can do stuff that you should not do at this stage of the game like getting th10 at lvl40. I had 1 kid in my clan that used 200-300$ to get th9 at lvl45. One pekka barracks, rest at lvl1 or 2. One xbow lvl1, but archer Towers lvl3, mines not upgraded, 2 builder huts and so on.

