Wow. So I assume that meesa shouldn't speeks like Jar Jar or yousa might have a heart attack. Just checking. Now, while it sounds like your problem is pretty out there--far far away, even--it's a more universal problem than we might imagine. It's a common communication issue: there's a topic about which you're very passionate, but those passions get the better of you and end up shutting down rather than encouraging dialogue; in some cases, make people think you're gonna go wookie and pull their arms out of their sockets. It's great that you are acknowledging that you can be abrasive and want to change that... first step to recovery. I sense the good in you.
While this isn't the typical "dicey" topic, it is useful to get a handle on. Considering the new trilogy did gross over $2.4 billion, you're likely to encounter people that did actually like these movies. Even though most people don't hold their views of Star Wars so dearly they need to keep a defibrillator handy, if you said "they were without a doubt the worst movies anyone has ever made," and the people you're talking to enjoyed them, then you are insulting their tastes and relieving them of any desire to talk with you... possibly about anything.
Now, to quote a little green puppet "control, control, you must learn control." Easier said than done. A good way to do that is to practice. And since we don't want to transform others into your verbal punching bag, I suggest you rehearse alone. Yes, my advice is to talk to yourself--just don't do it where other people can see you. The Jundland Wastes, perhaps?
Brainstorm ways of talking about the movies (the post-1999 ones) in a way that allows you to express yourself with conviction and calm. This is key to maintaining constructive dialogue on any heated topic such as, politics, gay marriage, abortion... and, yes, even an obsession with a Hollywood production. Try to stay away from hyperbole--superlatives like "worst" and "ever" should be avoided--and don't name-call (difficult when talking about the pompous, greedy, hack George Puke-Ass, but... uh... where was I? Oh yeah, no name-calling) and keep comments in the first-person. Talk about how you feel and what experience makes you feel that way. This allows for an exchange of opinion and clarifies that it is just that--your opinion.
For example, something like "I loved the original trilogy and had high expectations for the new ones that were not met. I was very disappointed." It is very clear where you stand and it's hard to argue with or take offense to because it's fully about you. Now, if the people you're talking to are not uber SW fans and liked the new episodes, then they can feel comfortable saying so. If they are uber fans and did like the new episodes, well then, you don't want to be talking to them, anyway. No, I'm kidding (mostly), but you have gently opened the door for further debate. While it may be harder to maintain your cool in an on-going debate, it is still important to do so--this is a good time to practice with another person as fans will likely be able to spar with you longer before taking offense.
I also recommend that you "search your feelings." Examining why your emotions run so deep can be a big step in learning how to control them. Plus, maybe--now this is a big maybe--you may discover that this issue really isn't worth getting so worked up over and will be able to better rationalize a calm before engaging in your next star war.
Being able to govern your passions so they don't overwhelm your ability to express yourself poignantly is an important skill for social conversation, or any communication for that matter. We want to show people who we are without intimidating them and preventing them from telling us who they are. Learning new perspectives helps us grow. Until you feel like you're able to control your anger in proper jedi fashion, you may want to steer clear of Star Wars-based discussion for a while and instead stick to the basics: "come to this cantina often"?