The performing enhancement drug that Mark McGwire took was Androstedione. It was not illegal nor banned from Major League Baseball until 2004 and Mark had been retired for five years.
McGwire didn't retire until after 2001, but regardless, there was a gap between McGwire's tenure and baseball making steroids and andro illegal.
I think the greater point being lost is that steroid-using ballplayers are being ripped for using a substance that wasn't illegal in baseball at the time, while ignoring that Babe Ruth used corked bats, where were definitely illegal when he played and are still illegal today.
(As an aside to cannonfodder, whether using corked bats helps a hitter -- the evidence is mostly inconclusive, mainly because there's a placebo effect involved -- is immaterial in the era when Ruth used them; there was no such technology to measure the effect, and the belief there was an advantage remains widespread to this day. See Sammy Sosa.)
I'm not defending the use of steroids. But it seems there's a great deal of gaping inconsistencies and ignoring of facts in the arguments about ripping into steroids-using ballplayers.