In the US, most employment is 'at will' and employers can and do fire without cause. In this case, a marginally sophisticated employer could readily cast what was written as justification for firing with cause. And because of the way unemployment insurance rates for an employer are set, the employer has a financial incentive for so doing. On top of that, those lawyers would have access to historic chat logs to back up the company's interests.

Of course none of that applies outside the US.