"so-called" means not real, just in theory but not in practice
"so-called equality" means that equality doesn �t really exist
"a long way off" means "far away"
drunk people "stagger" when they walk....they lose their footing etc
Now to get back to your sentence:
"so-called equality is such a long way off it staggers me" means that....
to be able to have equality will take so long that the author can hardly believe it...like this concept knocks him off his feet....
I hope that clears things up a bit for you :-)
Have a great weekend!
Regards from wet Thessaloniki