I suppose Toei should be commended for showing a progression in Roshi's predilection for molesting women, he starts out just being your typical old pervert, who gets incredibly embarrassed just requesting to see panties, boobs, puff-puffs, you name it, before daring to attempt feeling up unconscious women.
3 years later and kinda going hand in hand with his increase in power, he has no problem with foregoing the requests and just grabbing women's butts, whether that be Bulma or flight attendants and nurses even later on. He keeps at that level all throughout Z, where we even get further scenes of him grabbing Maron's boob, but she's a bitch and I hear she was out to get Krillin for insurance fraud?, so that's A-OK!
And then he grabs #18's boobs, but she killed millions of people in the alternate timeline, so that's the least she could give up for her alternate self's atrocities!
Finally in Super, Roshi has stepped up his game even further and as we find out he has also acquired unfathomable power, so it makes sense he would be so incredibly aggressive now to the point, where he doesn't even hide it anymore and just takes whatever girl he wants, despite their protests.
However knowing full well he's about to jump off a slippery slope, he decides to train away his perversions, so he doesn't get to the point, where he crosses that unforgivable line.
Even at Toei they realized he was just about on the verge of going too far, so they give him one last despicable act to make his training that more meaningful or something