Xenophobia is the fear, hate or mistrust of things or people foreign or alien to the sufferer. Some medical doctors believe xenophobia is a psychological condition, while others believe it to be a racist condition. People who suffer from this condition are known as xenophobes or xenophobic.
Several races have had encounters with xenophobia amongst their populations. On post-Xindi-ravaged Earth in 2154, xenophobia was more prevalent, with non-humans being attacked and the radical Terra Prime movement gaining support. (ENT: "Home", "Demons", "Terra Prime")
The Cardassians exploited their race's xenophobic tendencies by attempting to genetically alter soldiers to heighten this fear. The experiments failed, with the altered soldiers abandoned on derelict space station Empok Nor. (DS9: "Empok Nor")
The Bolian Isolationist Movement felt Bolians would lose their cultural uniqueness with Bolarus IX's involvement with the Federation and on-again, off-again conflict with the Moropa. Sometime after 2348, the Bolian Isolationists were exiled from their homes and founded New Bolarus. (Star Trek: The Cantabrian Expeditions: "Oh, What A Lovely War", "Howl")
Other xenophobic races include:
Speciesism, also known as Xenophobia, was a belief that one species was inherently superior to another or all species.
It was found in cultures across the galaxy, and for various reasons, ranging from religion and race to simply an overinflated sense of superiority. It could range from single individuals to the entire species. Some races, like the Gran and the Givin, were mildly speciesist, and still able to work with other races.
Others, like the Hutts and the Chiss, considered themselves inherently superior, but still managed to work alongside other races on occasion. Still others, like the Ssi-Ruuk, the Yevetha, and the Yuuzhan Vong, considered all other races an abomination. An especially prevalent type of speciesism was Humanocentrism. Some believed Zabraks to be speciesist due to their extreme amount of determination and willpower, although this was not true. A notable Human speciesist was Count Dooku, who considered all non-pure Human lifeforms to be disgusting and inferior. In response to such sentiments, aliens sometimes formed anti-Human sentiments. At its height the Galactic Empire was notable for its many speciesist policies and attitudes to certain worlds with non-human populations that could very easily be construed as speciesist. For example on the Planet Eriadu (the home world of the Tarkin family) the Empire legitimized the enslavement of Non-humans. By the time of the reign of Emperor Roan Fel, however, such policies had apparently ended, as evidenced by the presence of non-human stormtroopers and at least one alien admiral in the Imperial Navy. This was perhaps in response to a manpower shortage in the years after the Battle of Endor, as the realities of fighting a losing war led to the opening of the ranks to any sentient being willing to fight for the Empire.
In the English language, speciesism is a word describing negative or prejudiced human attitudes towards other species, especially nonhuman animals. It was coined by Richard D. Ryder. However, the attitude of speciesism that Palpatine possessed seems much more closely linked to Racism, which is the belief that people of one ethnic origin are inherently superior to people of every other ethnic origin.