How surprising is it when a person designs code in a very clear and impressive structure and just when you think about asking them for guidance, they reveal themselves to be complete turds?

I've been working with this person's "infra" code, at work. I've rewritten some classes to use their infra. I had a vague idea of how the classes work. I had no idea of how their code works. Expectedly, there were some issues but now only minor ones remain.
I asked them for a description of what I'm supposed to do for the few bugs I'm facing. They replied in such a condescending tone, it made me want to punch them through the screen.
Almost a month later, we're still going back and forth with emails. I've been swallowing it and responding calmly. I never got direct answers. Always deflections to irrelevant things or veiled insults. I took it because they did correct one silly error of mine that actually my code reviewer should've caught. (What's worse is that it got introduced by me just before my review and commit.)
But does that give them the right to insult me in front of the whole team including my project manager? I got a reply today from them with everyone of note in cc implying very clearly that I have not done any work. They highlighted a line from my code with some todo tag (that was not meant for them) to make their invalid point. A line that's unrelated to the bug I asked them about. This is after I proved them wrong when they insisted that I had done something wrong about a feature related to the bug.

If you don't understand what I asked for fucking ask me to ask again. But do not fucking try establish yourself on higher ground by pointing out irrelevant things in my code.
I was shocked and enraged that they'd do such a thing. I double checked everything like a mad man. Despite knowing that the fix has to come from them, I was instantly transported to the noob stage, grasping at straws. I wanted to send a really scathing reply right away but my manager asked me to wait.

My mind is now a see saw shifting between a panicked noob questioning every fucking thing I ever did in my nada life and a hungry enraged monster looking to maul that fucking shithead for burning me like that.

I’m just curious, how relevant is slack in the workplace? And is it enjoyable to use or awful like Skype