If you plan to run a business I hope you take it seriously enough to not fire anyone that hurts your feelings.
Let's not trivialize verbal abuse by calling it hurt feelings.
I'm not saying this level of seriousness is what happened here, but you exaggerate in the other direction.
What an employee says about their boss generally has zero implications on their career and lives, so long as it does not outright accuse them of a crime. When's the last time someone called you to provide a reference on your boss? I thought so.
In turn, what a boss says about their employees can be entirely career-ending and therefore life-altering, even if said in jest or later retracted. A higher standard exists precisely because the stakes are so much higher.
Even if you know the lines aren't blurred, if you perceive others acting as though it's up for debate, you're more likely to consider bad-faith appeals to the subjectivity of abuse as perhaps being in good faith. Few among us are philosophers capable of reasoning everything through from first principles, all the time, so these things matter.
Tone and body language are like 80%+ of in-person, verbal communication.
We need to be very careful to, as I mentioned, not “abuse” the term abuse to the point where it becomes meaningless. If everything is abuse, nothing is abuse, and we need to invent a new term.
As does some of the conduct that may lead to the counterparty calling you names in the heat of the moment.
You'll see plenty of it here on HN - some commenters are great at just staying within the guidelines while pushing others over the edge in frustration.
We don't take ourselves too seriously, and find people who do take themselves seriously worthy of some extra piss taking to bring them down a peg.
(Oh, and rm -rf'ing your HD *would* land you in very serious legal trouble. It is a criminal act under the Computer Misuse Act 1990. And rightly so.)