Nope they are different things
Nope. It was acceptable by definition if people accepted it. "Accepted" and "acceptable" are both derived from the same verb "to accept". |Sorry you don't like it, but you don't get to define the English language.
just because something was accepted at a particular time does not imply that it is acceptable.
That's true but you are glossing over the fact that you used two different tenses in that sentence.
"just because something
was accepted at a particular time does not imply that it
was acceptable.
"just because something
is accepted does not imply that it
is acceptable.
The above two sentences are both false (I omitted "at a particular time" because when you use the present tense, the particular time is now). Your sentence quoted above is true because attitudes have changed.