This is exactly it. The reason tech companies are so big on supporting regulations against ISPs is because those rules are narrowly carved out to not apply to them, eliminating a large chunk of their competition.
Imagine if this law also applied to Google and Facebook, and they couldn't charge more when you opt out of their data collection?
To use a physical analogy, ISPs are like roads. Google and Facebook are like places you can drive to on the roads.
You argument is essentially that it is not right to ban persuasive surveillance on the roads if it is possible for people to use those roads to reach destinations where surveillance is allowed.
That analogy is completely arbitrary though, and only drawn to serve tech companies' interests. Because Facebook and Google are platforms, not end destinations in themselves.
In your analogy, perhaps the ISPs are the highways, and tech companies are the neighborhood streets, but they're both roads. Because you're not trying to get to Facebook, you're trying to get to your grandma's photo album, that unfortunately you can only get to through Facebook.
You can only get to grandma's photo album because she put it on Facebook. She could have put it on Flickr, or iCloud, or numerous other places.
No matter which she chooses, though, to get to it a large number of people only have one choice for high speed internet access to go through.
ISPs are low level infrastructure tied to specific geographical locations. If you don't like the infrastructure where you live then generally you only way to pick something better is to move to another region.
If you don't like your photo hosting site, or you blog hosting site, or you online backup site, or your stock tracking site, etc., an alternative is a URL change away.
That's why different regulatory handling of ISPs and the places you reach through those ISPs makes sense.
Facebook is more like a bar or club or church in the physical world analogy than it is like a street. You go there to interact with other people who go there, but it is a destination, competing with other destinations that those people could meet at instead.
That said, Facebook does offer communication services, and so some regulation of communication services that makes sense would make sense to apply to both them and ISPs.
"an alternative is a URL change away" isn't really a true statement. You can move off of Facebook, but you can't move your friends and family off of Facebook. You can use a YouTube alternative to watch videos, but all the videos you want to watch are not going to be there.
Pretending platforms are a wholly different thing than infrastructure, and easily switchable seems willfully ignorant of the real world. Moving platforms is almost as difficult as moving real world locations. And popular opinion aside, most people have two or more ISP options. (I have three wired residential ISPs here, two offering gigabit connections, and at least four wireless carriers.)
Imagine if this law also applied to Google and Facebook, and they couldn't charge more when you opt out of their data collection?