Completely disagree, I play to have fun and to enjoy myself. If I play better and have more fun onstage with an amp, then I'm gonna use an amp. If I can enjoy using the IEMs a bit I might use them, but I'm not gonna sacrifice my fun and enjoyment the entire night just so a few clowns on stage can crank THEIR amps and do whatever they want.Playing with or without amp is not something that should influence good musician.
If everyone is using IEMs out of necessity then that would be different and I would have to assess the big 3s: music quality, band quality and pay quality. If 2 of them are met I'm usually happy and will "work" my music with the rest of the band, but If I was the OP and people were cranking their amps on stage, you better believe I'm bringing mine or they can find another bass player. The pay for most gigs ain't worth taking poopie from anybody nowadays in my opinion and I'll be happy as a clam playing and recording at home as long as I don't have to deal with "memememememe" clowns on stage that aren't doing their part to keep stage volume down.