I don't think you were being a jerk. I think you are right in what you said. (this is not pointed to anyone in particular) If you have graduated high school, or at the very least attained some grade level above 8th, you should be able to effectively write and use the English language. I am not talking about silly typos and spelling errors. I am talking about the very basic rules of English. (non usage of contractions, sentence structure, punctuation)
I know this is not English class. I know that a car forum is informal and laid back. Keep in mind however, that what you say, the manner in which its conveyed, and your attitude, is how you are perceived. I have friends who type like cavemen but are extremely intelligent. You'd never get a chance to share in their knowledge because you would automatically dismiss them as morons. On the flipside, my posting may bare some semblance to actual rule following yet I am a card carrying pudding sucker.
I know, who cares what other people think about you? Well, if you don't care, no one else will either. It's not about being Mr./ Mrs. popular. It's about receiving the respect and courtesy you deserve. It's what makes an enthusiast site such as this, that much better. You get out of it what you put into it. You type junk, you'll get it back.