Hi Wally, 
I always enjoy your posts. This one is no exception. 

I often find, especially when I am speaking at teachers' conventions and conferences, and even in some of my classes, that many of the people who choose to attend are there because of their own dietary interests, which are often at odds with my paradigm. Many of these folks wish to debate these issues with me. When time and opportunity allows, I try to thoughtfully counter their ideas with my own and trust everyone present to draw their own conclusions.  The rarest result is that some of the people who believe in a different paradigm are swayed to my thinking. Much more commonly, the others present are swayed. These opponents help me to hone my own ideas. And sometimes, they persuade me that I need to adjust my thinking. I have never seen such opportunities arise in the context of name calling and identifying someone's ideas as "rubbish". Whether they are vegetarians, fast food advocates, or high-carb enthusiasts, dismissing their ideas as rubbish is most unlikely to persuade them of the error of their ways and most likely to invite similar attacks. It moves the discussion away from a discussion of the merits of the opposing positions toward hurt feelings and a sense of being personally devalued. 

I don't see this as a slippery slope. I see it as my human responsibility to respond to people with respect regardless of our differences of opinion. I sometimes fall short of that ideal but I believe strongly in the merits of that approach.

Thank you for the opportunity to clarify my perspective on this. 
best wishes, 
Ron