Canon demonstrates that Snape was not a nice man, who bullied his students and embraced the Dark Arts, and who was a Death Eater. Canon also suggests that Snape held anti-Muggleborn sentiments as a youth:
‘There you go,’ he said, as Snape struggled to his feet. ‘You’re lucky Evans was here, Snivellus –’
‘I don’t need help from filthy little Mudbloods like her!’
‘Fine,’ she said coolly. ‘I won’t bother in future. And I’d wash your pants if I were you, Snivellus.’
Order of the Phoenix - Page 571 - Chapter twenty-eight, Snape's Worst Memory - Bloomsbury
Yet there is evidence Snape might not hold such deeply prejudiced beliefs:
It was night-time. Lily, who was wearing a dressing gown, stood with her arms folded in front of the portrait of the Fat Lady, at the entrance to Gryffindor Tower.
‘I only came out because Mary told me you were threatening to sleep here.’
‘I was. I would have done. I never meant to call you Mudblood, it just –’
‘Slipped out?’ There was no pity in Lily’s voice. ‘It’s too late. I’ve made excuses for you for years. None of my friends can understand why I even talk to you. You and your precious little Death Eater friends – you see, you don’t even deny it! You don’t even deny that’s what you’re all aiming to be! You can’t wait to join You-Know-Who, can you?’
He opened his mouth, but closed it without speaking.
‘I can’t pretend any more. You’ve chosen your way, I’ve chosen mine.’
‘No – listen, I didn’t mean –’
‘– to call me Mudblood? But you call everyone of my birth Mudblood, Severus. Why should I be any different?’
Deathly Hallows - Page 542 - Chapter thirty-three, The Prince's Tale - Bloomsbury
Dumbledore explains to Harry why becoming a Death Eater might appeal to a teen or young adult:
‘As [Tom Riddle] moved up the school, he gathered about him a group of dedicated friends; I call them that, for want of a better term, although as I have already indicated, Riddle undoubtedly felt no affection for any of them. This group had a kind of dark glamour within the castle. They were a motley collection; a mixture of the weak seeking protection, the ambitious seeking some shared glory, and the thuggish, gravitating towards a leader who could show them more refined forms of cruelty. In other words, they were the forerunners of the Death Eaters, and indeed some of them became the first Death Eaters after leaving Hogwarts.'
Half-Blood Prince - Page 339 - Chapter seventeen, *A Sluggish Memory - Bloomsbury
The above are just a few examples to consider. Snape held an incredible amount of hate in his heart, yet also a tremendous love for Lily Evans. When Dumbledore asks Snape in Deathly Hallows whether Snape's doe Patronus means Snape still loves Lily, Snape answers, "Always." I don't think it's a stretch to assume that, had Lily returned Snape's romantic feelings (Which J.K. Rowling has said she might have done), Snape would have jumped at the chance to make a life with Lily, her bloodline aside.
But would this have been in spite of Snape's prejudices, or was the young Snape who blustered and bullied and called all Muggleborns "Mudbloods" merely a front to impress a group of friends (the Death Eater crowd) whom he wanted to be part of?
Q: So what I'm really asking is whether or not Snape was truly prejudiced. Was he? Or did he just behave in an outwardly prejudiced manner, hoping to impress the group of up-and-coming Death Eaters, or for some other reason all together?
I'm looking for an answer from canon -- the 10 Harry Potter books, Pottermore, or quotes, interviews, or tweets from J.K. Rowling. A subjective answer in the spirit of canon is totally welcome -- please don't hesitate to put forth thoughtful theories. I am not looking for any information from any wikipedia. I don't reward the Fastest Gun In the West, so don't feel rushed. Also, if you need me to look over an answer you've left me for a different question, leave a comment with a link to the answer.