We have to allow all opinions.

Why? You don’t say.

We can’t prevent people from having abhorrent, evil, false opinions, but we can certainly discourage them from shouting FIRE in a crowded theatre by having laws and punishments.

There is no truth out there.

“So we might as well allow people to do whatever they want — rape, murder, kill — because how do we really know anything?”

Yes, there is. Not every statement is unambiguously true or false, but many are.

It’s all far too complex to fathom

For you. “Real world things are complicated! Best to give up immediately.”