[MavKikiNYC]

IMO:

I don't think there is any question that the company was well within its rights to dismiss this employee for inappropriate behavior at an event to which he was given access by virtue of his status as an employee of the company, and to which the company was given access by virtue of its relationship with a client.

Assault might not be the best comparison, but the employee's behavior need not be that extreme either.

He could've engaged in an inappropriate (belligerent, disrespectful, profane, etc.) discussion of politics on company property on company time in the presence of the client--grounds for dismissal.

He could've inappropriately interjected a political discussion into a meeting with the client, expressing views which he should've known would be offensive to the client and might jeapordize his employer's business with the client--grounds for dismissal.

He could've surreptitiously inserted a political message into an ad spot, with said message being in direct opposition to his client's views--grounds for his dismissal.

He could've inserted a political message onto signage that his company produced for the client, with a message that was in direct opposition to his client's views--grounds for his dismissal.

Or, he could, as he did, attend a political rally to which tickets were required, with tickets provided by a client, and conducted himself in a way that constituted an embarrassment to his employer, and which constituted offensive behavior to the client--again, grounds for his dismissal.

If this person wanted to express his political beliefs, he should've taken care to do so in a context where he was clearly doing so as an individual, not as a representative of his employer, and not as a guest of a client.