Should he be cast out form society? No, but I sure won't support him until I see evidence he disagrees with the most disturbing things associated with Trump: sexism, racism, etc.
We need to hold people accountable instead of making execuses for them.
Otherwise I feel like you're more interested in partisan political posturing than actually holding people accountable.
(for the record, I despise both Clinton and Trump, but had I been a US voter rather than a UK bystander, I'd've held my nose and voted Clinton on the expectation of that being the lesser of the available evils)
Same with racism against people form Mexico / middle east. Sadly comes down to a matter of scale, at least for me.
This sort of stuff should ruin someone running for president, somehow it didn't matter here.
But to get to the heart of your point "enforcing laws" Legality is in no way equivalent Morality. People use terms like "enforcing laws" as a sort of dog whistle to imply we should not and are not going to be listening to minority voices.
I think that the kind of people that surrounds you also tells something more of the person in question. And it's not only the figure of Yiannopoulos that is questionable in this particularly case....