alt Hacker NewsThey didn't say illegal, they said wrong. And they were right. You even agree with them by saying "It's not nice". Non-nice things are wrong in some way.
And, we already live in a world where website owners can legally dictate exactly what software you use to access their content. They can require that you log in with specific browsers running specific software on your computer, they way online schools run exam proxies.
We do not in fact live in that world. It is not illegal to violate the terms of service of a website.
A website can block Xyz user agent, put Xyz in robots.txt, or even put "No using Xyz!" in a popup and you cannot be prosecuted for using Xyz. It might be hard for you to evade their requirements, but it's not illegal.
Whether or not it's wrong is a matter of opinion. Yours differs from mine, that's fine.