Help me resist the dark side...

Try this,

1. as stated above, cease and desist trying to prove your point. This will just keep the frustration cycling.
2. Set aside your own opinions and values and accept the possibility that the other person's views may be just as valid as yours. Grant them the benefit of the doubt and basic respect that all people deserve.
3. Seek first to understand. Stop and listen, explore their rationale for their beliefs or decisions, ask questions about the terms you dont understand or the connections you dont see. Let them teach you about their experience.

In this way, you can maintain the relationship without sacrificing your own beliefs. You may never get the same in retun but this type of interaction increases connectedness between people which generally leaves everyone better off in the end. Plus they may come back later to continue the discussion.

An inability to rest until others agree we are right suggests a very concrete, "decided" way of thinking. You're right, they're wrong, and if they refuse to concede to your superior intellect there's no option left other than to duke it out until they agree with you - or, more likely, give up.

If something someone says challenges our preexisting way of thinking, and the only response available to us is to argue with them until they concede we are right (an unlikely outcome at best), it implies an inability to extend compassion (instead ask yourself "why might this person believe what they do?") an inability to compromise and incorporate new perspectives and understanding (ask yourself "despite appearances, might this be valid, or valid in certain circumstances?"), or perhaps even insecurity over the existing belief (ask yourself "why does this truth require my vigorous defence?").

You will always meet contrasting ideas to your own. Some will be from people with less or more information than yourself who therefore hold a different perspective, and more often than not the question will be a matter of opinion anyway. I find arguments and dispute are just about the least effective way of convincing anyone anything other than that you're an argumentative person - if you really hope to educate and enlighten with your knowledge (or, better still, wisdom), do so in friendship rather than aggression.

Finally I wouldn't describe this situation as the dark side as such... really it's just something you need to learn more about, and the fact you're asking questions and identifying the causes already suggests you're well on the path. You know this behaviour is wrong, now you just have to break the habit. I've been in your shoes. The best advice I ever got was "step away from the keyboard". Other people's opinions are just that

Some people might even see your point as more accurate/correct, and even actually agree with you without saying so - but choose to keep up the original position for some reason only, usually only, really relevant to themselves....
:S
I find the common reaction I have like this to be about self doubt - not so much in my own basis for my view but rather the extent of unknowns which might exist to influence what I know. The subconscious seems to invest energy (experienced as emotions) into reexamining the vulnerability of my position to being ignorant PLUS the potential results of being seen as ignorant... and that assumes my position as I understand it is actually logically sound in of itself, which can be tricky as complexity increases.

So its good not to let oneself get too invested emotionally at the outset in an argument IMO, as if any level of serious attention is going to be given then it runs the risk of increasing the scope of emotional involvement beyond ones preferred levels.

Thank you all for the sage advice everyone. Each comment had something good to take away from it. I will try to stop limiting myself with my own point of view.

Adder wrote: So its good not to let oneself get too invested emotionally at the outset in an argument IMO, as if any level of serious attention is going to be given then it runs the risk of increasing the scope of emotional involvement beyond ones preferred levels.

Yes, this. I think we get emotionally invested when our worldview (opinions, biases, beliefs) become our identity. At that point a different view becomes inherently threatening on a personal level. If we strive first to understand we may discover that we were mistaken or could be altered irrevocably. If we need to believe we are always right then this scenario is terrifying. But this fear never allows for change and therefore prevents learning and growth.

Teaching #4: Jedi are wary of attachments, both material and personal.