For many ideas, you can't really understand what your own viewpoint until you see an opposing idea and reject it. And you can't really consider why you believe what you believe until you have to defend it against criticism.

That being said, this kind of argument is only really useful in the right kind of environment, academia for example. Certainly not the vast majority of the Internet. And once you've thought about these things for a bit, there's not much value in continually exposing yourself to a toxic cesspool just to remind yourself that it's not for you.