Only once that I'm aware of - iirc, a British magazine refused to review our cd after someone on the board had written negative comments about said mag. We sort of shrugged that one off; for one thing, the comments were not wholly inaccurate.
Over the 40 years I've had my company we've had about 4 different distributors on the UK. None of them sold more than 50 of any title. Who would want to "kill free speech" to gain that? Not saying 50 sales are nothing, but weigh the consequences vs self respect.
I hate this shit when folks are afraid to say what they mean to "protect" commerce. I have undoubtedly lost sales for my uncensored comments here but I accept that and feel it's "their" problem and they lose by not owning some great music.
If I thought many posters to any thread were "holding back" to be "polite" I probably wouldn't be around long.