Astrology is bigotry
Astrology is bigotry is an argument which posits astrological claims are bigoted if the claim prescribes behavior to people based on when they're born. Although most people who become fascinated with astrology first see it as a fanciful and helpful way of understanding other people, they often fail to realize that they are becoming prejudiced, and often bigoted because of their supernatural beliefs.
Consider the statement, "I hate Chinese people because they're so irresponsible." Unless you're already bigoted against Chinese people, you would immediately recognize this as a racist statement because irresponsibility has nothing to do with being Chinese. Or, consider the statement, "I would never date a Jew, they're not loyal." Again, there is nothing about Judaism which makes someone disloyal, and, unless you already are prejudiced against Jews, you would see this statement as religiously bigoted. Now consider a type of statement frequently uttered by people who believe in astrology, "I would never hire a Scorpio, they're so dishonest!" Of course, what the statement is really saying is, "People born between October 23 and November 22 are dishonest." When stated like that, the bigotry becomes plainly visible.
I don't make such blanket statements
Obviously, people who believe in astrology don't think that everyone of a particular sign exhibits every trait associated with their sign all the time to the maximum level. They would never say, "All Scoripos are dishonest all the time, but rather, Scorpios tend to be more a little more dishonest than the other signs, so you have to be on your guard."
The problem with this criticism is, it only reduces the level of bigotry, the bigotry is still there. Imagine saying, "I don't think all Native Americans are dishonest all the time, I just think they're more dishonest than other races, so you have to be on your guard."
My past experience must be acknowledged
It certainly sounds bigoted to say, "People born between October 23 and November 22 tend to be more dishonest than everyone else," but, if someone has actually met several Scorpios, and they really have been more dishonest than the other people they've met, isn't there some truth to it?
Consider the statement, "I've met a lot of redheads in my life, and they always end up being more dishonest than that people with different hair colors." It may be true for a person that every redhead they've met up until this point has actually been more dishonest than people with other hair colors, but there is nothing about having red hair that actually makes someone dishonest, so this is just a coincidence.