I tend to find the best way to discuss things with people I don't happen to agree with is:

1. Agree on the same definitions for words that can have different interpretations.
2. Understand exactly the other persons idea/beliefs/argument.
3. Never resort to name calling or labelling (calling them 'a fascist, racist, bigot etc)
4. If you feel that they aren't listening, or refuse to try and understand your opinion then withdraw (life is too short)
5. Try and spend no more than 50% of the time talking.

I get into many very interesting debates with people, and have found regularly that I am wrong, and have changed my mind about certain things. I also fail regularly to adhere to some or all of the above on occasion. But trying to stick with these I find does help.

My personal philosophy is that I want to believe as many true things and as few false things as possible. Only by discussing things with other people, and expressing my true opinion might I achieve this.