You are correct. The poster was being rude and is a rude person. Unfortunately, while there are some decent people here, some of the rudest and nastiest people hide behind a facade. This takes some getting used to.
As with any new company you start with, don't always believe what you hear and watch your back. Rude posters, like this one, are the first to stick it to you, once you arrive. Some are managers in perpetual training and lying. They have to save their position at all costs. Some are trying to move to another area or get a promo or a trip. You have to make sure they don't get away with shitting on you. This is especially true if you are everything they are not and will never be. This will bring out the hater in a lot of people here, just the mere fact that you are a quality person. Think twice about coming to work here.