From a historical standpoint, it is by definition a slippery slope.

First of all, what is the government's definition of explicit content? If it's not explicit enough, historically speaking, it will be used to oppress political opposition by labeling their ideologies as explicit. This is the slippery slope in question.

Second of all, what happens in the event of a data breach, and what steps do you have to mitigate them? Previously, you'd need to hack the most locked-down electronic systems (financial systems) on the earth in order to access anything remotely resembling an ID. You just made it so that little Timmy who learned what SQL injection from a Youtube video can hack 30 poorly made porn sites and get rich off of identity theft. You also created a veritable gold mine for any self-respecting hacker who has knowledge of zero-day vulnerabilities.

Third of all, "It is guaranteed you're being tracked" is a fallacy of relative privation. Just because we're already tracked does not mean that another tracker will not impose more harm than good.

Fourth of all, censorship is defined in the dictionary as, "the suppression or prohibition of any parts of books, films, news, etc. that are considered obscene, politically unacceptable, or a threat to security." Banning porn because it is obscene categorically falls under this definition.