Do You Work With an Insensitive Jerk? [POLL]

When I was younger, my mother would remind me that I wasn't always going to like everyone I worked with. Personally, I don't think you ever have to like anyone you work with, you just need to work with them.

So here's a scenario I'm sure many working adults have been through, and I'm interested to see how it was handled.

Full disclosure: this is partially hypothetical.

Anyway, let's say Coworker A, we'll call him Robert, recently went through a life-changing experience -- the details of which aren't very important, except that it made him a different person. Robert's experience was something that Coworker B, we'll call him Mario, knew nothing about and simply wouldn't understand.

So, Mario spends a year teeming with bitterness about how Robert's changed but doesn't ever communicate with Robert, on good things or bad things. This ultimately forces Robert to have a very disinterested approach to Mario in general.

One day, instead of actually talking to Robert about what's bothering him, Mario chooses to tweet out a nasty, veiled comment about Robert and the way he acts.

So I ask you, is this workplace bullying? Is it just a case of an insensitive coworker? Or is it ultimately something that speaks about Mario's own person issues? Who's in the wrong here -- Robert for struggling to balance his work and personal lives or Mario for choosing to attack Robert from behind a computer? I'll leave that for you all to decide.