But if they're profitability involves alienating me as a user then I'm going to be alienated and I'm going to act like I'm alienated. I think the outrage makes perfect sense in this case. I'm equally outraged at other companies doing things that manipulate their customers for a tiny bit more profit (like shrinkflation).

Ironically they could have turned this situation into profit from me as I'm happy to pay for Reddit if it was required to allow me to use it in the way that I'm accustomed. Instead of embracing me as a customer, they want me gone.

In the end, it's their site and their decision to make, but it's understandable many people are upset by their actions and no longer want to use the site (which, btw, even if you were using it for "free" you may have been contributing in other ways via posts, comments, moderation, etc).

It also means losing potential customers - I would have been willing to upgrade to Reddit Premium to continue using Apollo, for example, but now I wouldn't even consider it.

While that's not false, look at it the other way: I've provided content for a private company for years, taking zero payment. Millions of us have. Reddit lives and dies by user submissions and comments, and taking what seems to be a stance that's wildly hostile to users feels very foolish to me.