As a commenter, there are several "good faith" ways to respond to this:
- I disagree, this is not harmful to these users, because ____
- I agree that this is harmful to these users, but that is outweighed by ____
- I don't know whether or not this is harmful to these users, and I'm looking to learn more about their concerns.
You seem to have taken another route, "I don't understand this concern at all, nor do I intend to educate myself on it, and instead I'm going to rant about how these people are bad for society". This doesn't strike me as productive.
(Also: you're arguing against an imaginary position. Nobody is claiming that Tumblr doesn't have the right to decide what content is allowed on their platform. The argument isn't that tumblr can't do this. This is just shedding a light on the harm this decision will cause)