I know the horse is dead, but I am going to give it a kick just the same...
Here is the problem with posting on RC, folks who do not know you will read 'into' your words and pick up certain connotations that may not be what you intended. I, like some of the folks here, never met you in person and instantly thought - 'wow, what a dick!' after reading the post and just passed it over. I do not think its a MARS thing because really on RC its pretty one on one and I see very little being influenced by the local reefing club.
I can relate to your experiences all too well, and I think most of us have been there a couple times. I am sure you are indeed a nice guy, but at the end of the day its YOUR job to woo me, the potential buyer who has never met you and buys way too many tanks in the first place, and that is not the way to do it in my book. You could have just said, price is firm and got your point across just the same.
Again, not knocking you, just providing some constructive feedback from where I stood and not knowing you personally. As much as it pains me repeating much anything my father once said, "Its not what you say... but how you say it." - especially in written form, where the other 90% of communication (body language) is not there to bring the point home.