Great question!

I talk about this in greater detail here, but the more accurate description is that social progress on mutant rights gyrates wildly, depending on the direction that the writing and editorial staff want to take with the X-Men. So for example, you have a story where all of the sudden 70s America reacts to mutant-hunting robots tearing up midtown Manhattan by suddenly engaging in a wave of anti-mutant hysteria, as opposed to a wave of anti-robot hysteria. Later on, you’ll have incidents – the X-Men saving Dallas in full view of the TV cameras in Fall of the Mutants, X-Factor saving New York from Apocalypse – that significantly reduce anti-mutant hysteria. 

What you don’t have is much consistency about how social progress is going, because the X-Men hasn’t historically been a book about social movements. As I’ve discussed in that link, the X-Men engage in a particularly elite form of politics, primarily centered around debates, trials, and press conferences, and we don’t really get to see much in the way of social movement organizing. The 1970s were an era of massive social movements of both the right and the left, you’d think you’d see some mutant rights groups organizing on college campuses, liberal big cities, protesting the Registration Act, pushing for a Genetic Equality bill, arguing in the courts that the 14th Amendment covers mutants, etc. Hell, you don’t even get mutant neighborhoods or mutant culture until Grant Morrison’s run. 

Now, related to this is the problem of Marvel and the future. Especially in the case of the X-Men, Marvel has a hard time imagining a future that isn’t dystopic – either anti-mutant dystopic or mutant-supremacist dystopic or Terminator-by-way-of-Apocalypse dystopic – which I admit makes the Dream seem a bit futile, but only really due to a failure of imagination. I’d be really curious to see someone clever take a run at a future America where the majority of the population are X-positive, where superpowers are so common that the distinction between superhero and civilian breaks down – and before anyone says that won’t work, let me point you in the direction of Alan Moore’s Top 10.