I just find it highly IRONIC considering the exact same approach has been repeatedly used to discredit people on the ‘other’ side, for distasteful and innapropriate behaviour, whilst simultaneously upholding others with similarly atrocious backgrounds as if they are a paragon of virtue.
But it comes down to what role they play, what they did wrong, how long ago and what they're doing now.
All situations are not equal.
An elected official should be held to a higher standard than a private citizen, even if that citizen is well know. There is an element of hypocrisy involved in politicians evading tax, claiming expenses and taking drugs. They are making the policy that will punish you for doing exactly the same as them, whilst they get away scot free. Hugh Grant has no hand in the making of public decency laws. Even if actions took place before they became politicians (and we believe they stopped the moment they were elected) they are still responsible for creating policy around things that they thought were absolutely fine to do themselves, but will throw the book at an ordinary person for doing the same.
Then - if they are found to have done something dodgy in the past (like conspiring to beat up a journalist) - and are currently cheerfully overseeing crippling austerity or a rise in hate crimes, then it all can be taken as a whole: to paint a picture of a person who is morally corrupt, lacks a conscience and believes in harsh rules for others and nor rules for themselves.
However, if they are now campaigning against the above - warning people of the disaster headed their way (despite being rich enough to ride out a catastrophic brexit perfectly comfortably, rich enough to live abroad if needs must and rich enough for private health insurance) then you can remember the bad thing they did, but also accept that maybe they have moved past that, grown up, changed.
I'd like to think anybody can change and I hate to think that anybody was forever damned by their actions 25 years ago, if they now seem to be well beyond all that.
The 'other side' are not well beyond all that. They're still doing it - it's part of a pattern of who they are. Yes, Boris is having things he wrote back in the 90s thrown in his face - but 'letter boxes and bank robbers' was not 25 years ago.
That seems an obvious difference to me - and not in the least an ironic bout of hypocrisy. No one is morally pure, everyone has made a mistake or done something wrong ... not everyone continues to do the same, and not everyone is then responsible for policy around their wrongdoing.
pretty simple stuff.