The Roma are hated for exactly the same reason as the Jews were, that is, because. Except the Roma are/were even less accepted than Jews, and as such had to resort to crimes to survive (the three career lines Roma had to choose from in Sweden were criminal, travelling horse-breeder, or travelling
tinker and knife-sharpener. Of course, their horses were always bad and they were trying to cheat you (so it was okay to cheat them back, pay underprice or even refuse to pay them at all).
So yeah, not surprising to anyone, the Roma ended up having to resort to crime a lot, which made the whole stereotype a circle and self-fulfilling prophesy ("He's a thief so I'm going to force him to steal to survive"), and over time, parts Roma culture became very intertwined with criminal behaviour. Compare to gang-culture in the US. Attempts have been made, up here in the north at least, to break this circle, but Roma are very suspicious and even hateful of government officials and organisations by now, and understandably so after having been treated like shit by every government for the last ~300 years - including the decades when racial biology dominated and Roma were forcefully neutered and had their children stolen and replaced into "proper" families in order to keep the race clean. In central and eastern European countries they're still often forced (not officially, of course, but the Roma knows what happens to those who step out of line) to live in ghettos outside the actual towns, and in poverty, with all the problems that automatically brings.
So it's a complicated situation, but their hate of Roma are definitely
exactly the same as antisemitism. Remember, Hitler didn't like Roma either - they burned in the camps just as well as the Jews did.
And yeah, don't call them gypsies. It's the same as calling Jews "kikes" or "heebs".