> If I understand your question, yes. I would join such a Subreddit because an echo-chamber isn't what I seek.
Good.
> I completely agree with forbidding things like doxing or making threats of violence but I'm concerned that "Safe spaces" only encourage intolerance towards other points of view.
Now now. If I went on /r/the_donald and started leaving comments about Gun Control, Trans Rights and Abortion, you and I both have a fairly good idea what would happen.
How do I know that? Well, a giant Pepe the fucking Frog fills half the screen when I even load the page, for a start, and I literally cannot upvote in /r/the_donald until I click the frog and subscribe. It's the online equivalent of a pub hanging a sign on the door saying who it welcomes in. Sure, you can ignore it, but are you really going to?
It's a de facto safe space. In fact, it's not even really a de-facto safe space, given Rule VI of The Donald is "This forum is for Trump supporters only." and if rule VII - "No linking to other sub-reddits" doesn't make it an echo chamber, I don't know what does.
Likewise, If I went on a Democrats subreddit and started raising Republican talking points, I'd be shown the door pretty quickly.
The issue isn't "pro" or "anti" safe-spaces, because everywhere is a safe space to someone. It's when people start to get selective about which safe spaces they're going to allow that gets to people.