No. Nothing reddit is doing is illegal. When you sign up for a service like reddit, there is a TOS, which allows them to ban, warn, limit interaction, etc, at their discretion when terms of their TOS are violated.

If their TOS doesn't allow pictures of butterflies, and you post pictures of butterflies, you will receive a warning. Continue posting butterflies, you'll get banned, until eventually receiving a permaban. There is absolutely nothing illegal about it, because their TOS specifically states no butterfly pictures.

they preach tolerance but are ALWAYS the ones to start the abuse, insults, name calling and threats when they are disagreed with.

First off, the group that I've always experienced starting with outright hate and name calling has been the right. Look at two protests, one by leftists, one by the right wing, on the same issue, and you will almost always find the most aggressive, slur using, name calling people on the right making themselves known far before anyone on the left will actually start doing anything even remotely similar.

And secondly, tolerance doesn't work when dealing with the intolerant. Consider this: Hitler is a brand new figure, comes into the public square, and starts preaching his views. Do we tolerate him, or do we not tolerate him? We should tolerate him, because after all, tolerance is good, right? Well, of course not, because his ideology is intolerant, and directly attacks the tolerant, extinguishing them from society.

The only way you maintain tolerance is by being intolerant of intolerance.

If a conservative states that trans people shouldn't be allowed to exist in public spaces, and the left shuns that person and ostracizes them, the left is being intolerant, but so is the conservative, who if they had their way, would have then eliminated far more presumably tolerant trans people from public life, if given the chance.

However, conservatives will then frame this as the left being intolerant, and act as if it's some kind of hypocrisy to try and preserve tolerance by being intolerant of intolerant ideologies.

On a place light Reddit most subs will just ban you for showing any right leaning opinions.

Because many subs have moderators that respect marginalized groups that are often the ones attacked by conservatives.

If someone comes into your community, and begins spouting off an ideology that's explicitly harmful to members of that group, the most tolerant thing a moderator can do when given two choices:

1. Tolerate the conservative and let them spout hate
2. Don't tolerate the conservative and prevent them from spouting hate

is the second, because otherwise your community is now persistently allowing in someone who is intolerant of the others in the community.

That is because "the left" might have a few members that just so happen to be better read and have considered some of Popper's writings.

On such a note, I presume these right-leaning opinions aren't about the virtues of conservative fiscal policy?

There are many right wing views, views that are now sadly becoming more and more mainstream, that should not be tolerated. If right wingers had faced actual consequences when espousing their hatred of minorities, we might not be looking at a US government that wants to cozy up to Putin and distance their long term allies while stripping away the rights of US citizens.