Strongly disagree, and I've got hiring evidence on my side (former subordinates going to work for friends, and said subordinates didn't know of the relationship) after airing some pretty reasonable grievances when I hired then and when they worked with me.
Of course, there's a scale. "I don't like their tech decisions"--yeah, that's an eyebrow raise, unless there's some real meat there. But I'm never going to judge somebody poorly for saying plainly that they felt disrespected or mistreated at a job, because it's happened to me too.
It doesn't matter if their grievances are legitimate or not (and you have no way to tell if they are). It's bad form to trash talk one's former employer or ex.
It's not just me. You will often talk yourself out of getting hired and many will not pursue a relationship with you if you indulge in it. There is nothing to gain by engaging in it.
It's not just you. Virtually every article I've read on interview tips gives this same advice. Speaking negatively about your former employer always reflects negatively on you.
Of course, there's a scale. "I don't like their tech decisions"--yeah, that's an eyebrow raise, unless there's some real meat there. But I'm never going to judge somebody poorly for saying plainly that they felt disrespected or mistreated at a job, because it's happened to me too.