It's not quite like that.
Bizarrely this started as a joke on 4chan (an 'anything goes' website, with an excess of right wing young men), but it's now been genuinely picked up by the far right, so whether it's offensive depends on the circumstances.
Clearly if you or I made the gesture to signify all was ok, then people getting het up would be ridiculous, but if someone is using it to signify white power then it's genuinely offensive - a bit like making a nazi salute. You would hope that if someone is being sacked, then the employer has a clear understanding of the context.