If your goal is to get me to change my mind about the series/book/author, you shouldn't just say "You're wrong" in an insulting way. You should give me some kind of thoughtful reason, listing some of the positives I may have overlooked. Same is true if your goal is simply to present a counterpoint to my review in the mailbag. If you really care about it, be my guest. If you don't, then from my end, it looks like you're just spouting off for the sole purpose of venting anger at me. Hey, it's a free country, but don't expect me to show you a lot of respect in return. If I don't have any respect for your opinion, then I'm that much less likely to consider your favorite author in a positive light, in which case I ask again, what is the point of your message?
Oh, and one other thing, if you're upset about the political views I may have expressed here and there, stuff a sock in it. :)