The word "rational" is usually considered the opposite of "emotional" and fear is an emotion so, on the face of it, it might seem that to speak of a "rational fear" is an oxymoron. This is only the case if the two really are opposites and many would not agree. Aristotle is one of them.
He points out that reasons should always rule, and that includes ruling the emotions. That would put reason over emotion and not necessarily in opposition to it.
A rational fear, as opposed to an irrational or emotional fear, would be one that is based on good reason(s). For instance, fear of leaving a candle burning when you retire for the evening is a rational fear - since it's likely to burn down the house in which you're sleeping. An irrational fear would be a fear of sleeping with fewer than four pillows - at least unless there's some good reason that you NEED four pillows to sleep safely (not fall off the bed, for instance).
Concerning a race of people, there can be no rational fear. A rational fear is based on experience and we don't (and can't) have adequate experience with enough members of a race of people to have good reason to fear them.
Concerning groups of people, the answer is not as clear. It is rational to fear murderers, for instance, even if we've never met a single one of them, because of the very thing that defines them as a group. It isn't rational to fear all gang members, as they aren't all criminals or otherwise "bad" people, but it's certainly rational to be very cautious of them since so many of them are and we have no way of knowing which specific ones there wouldn't be good reason to fear. Fearing people who are members of a large group is seldom rational, since there are going to be all kinds of different people in that group. The groups of people who identify themselves as atheists or Christians, as Democrats or Republicans, as single people or not - all of those groups are too large to warrant fearing them all, e.g. fearing the whole group.
Roughly, a "rational fear" is one for which there are good reasons, instead of being based on emotions without considering whether those emotions have any basis is reason. The better the reasons to feel the emotion, the more rational the fear; the weaker the reasons to feel the emotion, the less rational the fear.
Magophobia
Fear of Asians is called sinophobia.
fear to mingle or to move or to speak in mobe or group of people
If fear of gays is homophobia, then fear of straight people would be heterophobia.
Gerontophobia - fear of old people.
Of course not, there is no rational argument against homosexuality.
Anthropophobia.
Sociophobia.
A phobia is an irrational fear. Since it is perfectly rational to be afraid of sharks, that would not be considered a phobia. Sharks actually are dangerous.
Fear of people is called anthropophobia.
The completely rational fear of lady birds :)
Nomatophobia