I have dropped groups for the dps doing this. I find it highly insulting. I'm either the tank all the way through it I'm not. I refuse to run with DPS who only let me fulfill my role when they deem it necessary. I will not be the meat shield you only pull out for the boss fights.
Maybe he felt like there's no need for any tactics on trash. I wouldn't be so bold to do that in ops, but in FPs, when I know it will make zero difference, I'll pull before tank without thinking twice.