>You can't have an honest discussion when not everybody can speak their mind.
Yes, you certainly can.
Looking through the thread I see a lot of what appears to me to be honest discussion, and I would also consider it of reasonable intellectual level. Those common "unspeakable" opinions you allude to tend to drag the quality of discussions down, rather than lift them up.
But if it helps, everyone is aware of those opinions, it's just that most people just don't find them interesting or worth discussing.
Y Combinator co-founder Paul Graham has this to say on that trouble:
http://www.paulgraham.com/say.html
You can't have an honest discussion when not everybody can speak their mind.