Nope. Not at all.
Lots of people will use the excuse that their comments are true, correct, or legitimate as justification for ignoring that their actions have consequences. But, being right doesn't give you license to be a jerk. If you have legitimate points to make, they can be made in ways that aren't dogpililng and throwing excessive negativity around.
Basic rule of communication: however legitimate your point is, that point is lost if you don't deliver it properly. Delivery that makes the recipient stop listening is not useful.
Their credibility problem is not a legitimate excuse for less-than-grand behavior on our part.
I imagine, in fact, that our overly critical approach to dialog helped *create* that credibility problem. We have given them a good reason to not feel safe with being entirely open with us. Anything they say gets ripped apart, and we are unforgiving. That leads them to avoidance behaviors and having to try to cover their butts and doublethink when they do try to get us information, and that leads to credibility issues.
If you've ever had the thought that others should cut you some slack... well, then you should cut others some slack as well.