[cptskippy]

I think what she's trying to say is that while firing the individual is an easy solution, it isn't the best solution. In fact I would say it has a number of negative consequences for the employer beyond the cost of losing the employee.

Firing the individual without an investigation by HR sends a message of zero tolerance to intolerance (an intolerance of intolerance) to every other employee in the company, that any employee faux pas is utterly unacceptable. This would create a guarded work environment and have negative impact on the culture.

The two employees agreed to take the conversation from a work platform (i.e. Slack) to a personal platform (i.e. Whatsapp). To me this is akin to asking someone in the Office break room if they'd like to get coffee at Starbucks, it's asking to broaden a relationship beyond the scope of coworker. At this point the scope of their relationship (i.e. work related vs personal) is nebulous and I would argue broadens the scope of acceptable conversation.

From what little we know, it sounds like it wasn't unreasonable for him to think the bounds had been extended and also the guy grossly overstepped his bounds. In that regard, firing him summarily might be grounds for a lawsuit.