It's not about someone's private life at all IMO, it's about hypocrisy whereby there's moralising & judgement made on others, especially when it comes to arguing laws and issues of concern, where there's a conflict between the public facade & the private hypocrisy. The labour MP who was caught out paying for male prostitutes while arguing against legislation that was about prostitution springs to mind (I'm struggling to remember his name now).
And in the SNP's case, making a huge case of alleged inappropriate behaviour of one person (for what could be argued is political expediency, even if that's maybe not the origin of where complaints came from initially) while there's now allegations of covering similarly inappropriate & worrying alleged behaviour - with the only difference being who is under the 'good graces' of the leadership of the party - allegedly.
I loathe hypocrisy. Really loathe it. And right now, the SNP reeks of it.