[mithr]

Not intended as a straw man, but rather as an illustration that the same general opinion ("the idea of sanctuary cities has been taken too far") should be a perfectly fine (even if unpopular) thing to discuss in the workplace if your opinion and reasoning behind it are not derogatory, but not at all fine to discuss if they are.

[RestlessMind]

But thats the problem. Nowadays, saying "the idea of sanctuary cities has been taken too far; nations should have full control over their borders; immigration laws should be enforced" would not be a safe thing to say at my workplace.

[mithr]

Then I think your workplace is in the wrong in this situation. Reasoned discussions not based in bigotry/xenophobia/etc, where both sides are respectful, should definitely be acceptable at work -- they definitely are at mine.