If lives are ruined, it is the harrasser's own doing. It is precisely the fact that such incidents are routinely shrugged off that harrassers feel emboldened to continue. Perhaps if they realized their careers were on the line, they would check their hormones and act more appropriately.
Furthermore, this line of thought completely ignores the lives and careers that the harassers have already ruined. By treating junior colleagues as sexual opportunities, this robs the field of future talent by pushing them out.
I would disagree that an isolate incident of inappropriate touch or a suggestive comment or attempt to initiate a sexual relationship with an underling would ruin the victim's life or career. It is a different story if it is proven that the harraser also ignored the rejection or if they used their position of power to pressure the victim for example by threatening to ruin their career. Not differentiating between these two scenarios would not be fair to the harraser in the first scenario and it wouldn't be fair to the victim in the second scenario.
Which is why there are documented murders that people who were in danger of getting hit with academic sanctions committed to prevent those sanctions. Even if secret, the people imposing those sanctions are the ones deciding over the future career of the targets of those sanctions, so secrecy does not matter.
What I mean to say is that, firstly, there will be extreme reactions from individuals to any academic action against them. Truly extreme. At the very least they will blow up any cooperation there might exist. Second, everybody else will understand these extreme reactions, because they are justified by the ridiculous cost these sanctions impose on them. Addendum to the second one: often the supporters of people getting accused will threaten imposing sanctions on students of the professors going against their students, if they consider them valuable enough, for the more vague accusations (like plagiarism. Since technically having a single formula in a presentation unattributed is plagiarism, and everybody constantly does that, ... What I mean to say is that there is a LOT of "usual" plagiarism for more basic things and also a lot of accidental plagiarism, which results in that if you're a member of an academic board, you can bring this charge against virtually anyone at almost any time. Add to that that a lot of professors also have cases of less-than-accidental-but-currently-unpunished plagiarism to their name. Things that they committed where the victim couldn't bring a coherent case, but any of their colleagues certainly can construct a coherent case on behalf of their victims. So with one supporter in an academic board, you can get away with a lot. Without a supporter in an academic board, you're career can and will be torpedoed as soon as anyone in that board thinks it'll help them in some way to do that)
There are 100 academics, minimum, for every position available (which is one reason why so many "little positions" exist, like board members of conferences). That means one flaw essentially means you don't have a shred of a chance to achieve anything.
This means there are no "light" academic sanctions, and the result is that like the medival and muslim punishment for stealing, it causes extreme responses. It means that a thief in the middle east will shoot up a market rather than be arrested for petty theft, and it means a grad student will sue a university for millions to avoid a little note on their diploma saying he got suspended for a week for destroying some university property.