In the new Star Trek 2009 film directed by JJ Abrams, young Spock was continually ridiculed for having a human mother. Certain peers in school even went so far as to call his father a traitor for marrying a human. This seems to be in direct conflict with the Federation's basic ideals of acceptance and tolerance. And if the Vulcans hated humans so much, why would they ever establish an alliance with them?
The Spock-childhood scenes from the 2009 movie were based on the equivalent scenes from D.C. Fontana's "Yesteryear," a 1973 episode of the animated series. There, the children call Spock a "barbarian" and say his father "brought shame to Vulcan" by marrying outside his species.
Children can be extremely cruel and intolerant toward anyone different from what they're used to. If they're raised to believe in certain social conventions, they can be ruthless in shaming anyone who doesn't fit them.
But we saw Vulcan prejudice against humans among adults as well in "Amok Time," when T'Pau seemed scornful of Spock's choice to bring humans to a sacred Vulcan ceremony. Even Spock himself purported to be insulted when compared to a human, although he was presumably joking. We saw other portrayals of Vulcan condescension toward humans in later series, notably the overt Vulcan supremacist Solok in
Deep Space Nine's "Take Me Out to the Holosuite." And of course
Enterprise showed that such Vulcan attitudes toward humans had been even more pervasive in the 22nd century. But it's been part of the franchise for almost its entire history.