I say exactly what I think all the time and have never had a problem with it. If "I think this is stupid" is all you can come up with, then the problem is with

I say exactly what I think all the time and have never had a problem with it. If "I think this is stupid" is all you can come up with, then the problem is with you. You can simply say "I think we should do X instead because of Y and Z" and get the same exact point across. You're still being direct and not skirting around the issue at all. It's not even about caring about other people's feelings because it's the right thing to do or whatever. It's just a more productive work environment. Attacking people personally triggers defense mechanisms in their brain that almost always lead to bad outcomes. The overwhelming majority of people have brains that work like this, and denying that reality is not going to lead to anything good.