If you have that happen to you I recommend reaching out via DM either to your instance's admins or the admins of the server their community is on. Give them the context of the report and also explain how that mod reacted. If a mod acts like that they are very likely an abusive moderator, so make sure to let admins know about that.

If your description of the events is accurate: that's a shitty mod, and a good example of what I wrote in the last paragraph. We should be denouncing this sort of crap, and avoiding comms where it happens.

It’s not always so easy to assume that mods are going to be fair. Reporting people comes with a risk.

I'm not assuming that the mods are going to be fair. I'm taking into account that shitty mods do a favour to you when they out themselves, as they're basically showing you which comms to avoid.