But the man in the comic assumes there is no issue at play.

hijacking affiliate codes is unethical and should be stopped but don’t actually affect me in any way.

I mean, alright. But you could say “I don’t care” about any infraction of freedom and/or trust. I trust software to not modify my intent, any software that does so without asking can not be trusted in any way.

The affiliate link hijacking was not opt-in. How could anything remotely like this be accepted in a privacy focused browser?

When Firefox had the mr robot extension incident everybody was (righfuly so) mad, but that was way less damaging than altering users’ intent.