What's the deal with all of the negative references to this man? Didn't he jumpstart Desi's career in real life?

I don't know if he helped him, but he did give him a job and he was very cheap, so Desi figured better to starve on his own than still starve working for him, what negative references? Xavier used to go on talk shows with his young wife Charo and was always entertaining, funny and was indeed very talented.

It's just tongue in cheek when Ricky Ricardo makes fun of Cugat. I don't think there were THAT many references to him, were there? I mean nothing to get your pantalones in a wad over. :D

Desi was always grateful to Cugat for giving him one of his first chances and for letting him go form his own band;even though he was still dying of hunger anyways. There was one occasion that both Desi's and Cugat bands were playing on the same place and when Desi spotted Cuggie he called him a 'peasant' but he clarified that he was only joking about it since he was the one that put him there in the first place.

Oh, you meant references on the show, sorry! It was a comedy show, so they did comedic lines all the time, and anybody who knew his background would laugh at those jokes. And back then, everybody knew Desi's history.

There was a line in the episode when Ricky fought the new next door neighbour after they moved to the country. He was being booked to appear on a TV show, but after the spat over furniture they were going to get Cugat instead. That's what kicked off the fight in the end! It was all meant fondly enough I should think. It's just like Morecambe and Wise joking about Des O'Connor's singing.

There is also a line on the Scotland episode about Cugat. Lucy takes out and old Lp from Cugat and Ricky throws it away 'pretending' that couldn't be

A little of the subject, but wasn't Xavier Cugat married to Charo???

Yes he was, it was mentionned by me a little earlier, they would always go on talk shows together and were very funny and entertaining.