Being opposed should be encouraged even if it's just a way to internally test ideas; being obnoxious should be discouraged.
You, your team and your manager should be able to make that distinction. If work at a place where disagreement is systemically taken personally, look for another place to work at.
The problem is that if 9/10 have a bad idea, the 9 decide whether the dissenter is simply opposed or obnoxious.
Or it could be that only 3/10 have a bad idea, and 6/10 are afraid to side with 1/10 out of fear of likewise being considered obnoxious.
Any filter on honesty is a hazard IMO.
The lines between "opposed" and "obnoxious" are very blurry and depend a lot on whether the respective person is very socially adept or not.