So ignoring the point seems to be a strong suit for you.
You do not want to address the fact that you are condescending, so you put on your grammar Nazi boots and spin it as would a politician.
Message Boards and forum are set up for people to visit, exchange ideas, ask questions and yes to have a little fun. Most people do not get all auto correct and punctuation crazy on a message board that is already littered with emoticons and acronyms. Most questions and responses are short and to the point.
You called yourself arrogant. Thank you for doing that as I do not call people names, but I do love it when one self admits to their fault, even if they think it is a good thing.
I will not debate the importance of grammar on signs, because we all know it is important and if you do not think so you will not last.
Most use this message board to learn, to share, and to interact with other professionals in the same types of businesses. You spend your time on this board simply reading through post after post until you find something you disagree with and jump all over it. You are a keyboard ninja! Yes, opinions are important, but so is tact. You lack anything resembling tact. If you do not get the praise from others, you give it to yourself and tell everyone how great you are and bluntly that they are stupid.
I have come across others through the years that are as unpleasant as you. Usually they were people who started out in some business humble, eager to please, and motivated to do well and win over customers. Their business grows the money flows, and suddenly they think they know everything, and they feel superior to everyone else. On the other hand, I also know many people that have taken the same path and done well with their businesses that remained humble and polite. They also share their knowledge in friendly tactful ways. Those seem to be the people I focus on in Life and value as friends.