I just thought I would add an example that everyone can understand:
My Rabbi holds that Dagim tuna is the only really kosher one, due to issues with dolphins. Therefore, I cannot eat starkist or bumblebee or chicken of the sea or any others. For me, its not kosher.
HOWEVER, I respect that other poskim hold that the other brands are ok. So while I cannot eat it, I do not look at anyone eating it and think “Oh they are eating treif.” All I think is that they hold by a different (yet valid) opinion.
Does that make my point more clear?