This is kind of a 'fred about a fred' as the long running vegetarian parents thread got me thinking. How do I think my kids might rebel? How will I deal with it? How will my much more sensitive DH deal?
My parents did not hold back their opinions when I expressed my desire to become vegetarian - I would have been disappointed if they had - part of the 'thrill' as a 15 yo was transgressing. They were so bloody permissive - socialist/ atheist / let me go on a weekend to Manchester to see the Happy Mondays with my friends aged 15... that finding something they might vaguely disapprove was hard work unless I wanted to complete break from their values and join the army/ find religion/ vote conservative - which I had no desire to do.
I did not become veggie to shock my parents I did because it made no sense to me to be against animal cruelty/ testing and be environmentally concious and not at least consider cutting out meat. It was hard in 1989 and on a tiny income to be vegan but I did reject leather shoes unless they were second hand so I tried to be 'true' to my beliefs. I really credit my parents with giving me the confidence to be politically aware and active - so it was less of a rebellion and more of a tribute. I don't think they were perfect but by modelling a strong and meaningful moral and political framework in their lives and opinions they taught me how to make decisions about how I wanted to live my life.
I want my kids to have the same ability - I don't want mindless observance - they should have the confidence that I was given in my ability to think for myself - it is not their fault that I happen to be right! 
So if you think the way you live and your politics/ religion etc. is "right" how can you hide disappointment when that world view is rejected. I mean it will be bad enough if my dc deride my musical taste/ love of cats (animal not musical) whatever but I will cope with that
but other more fundamental differences - I cannot say I will accept and smile - I am not talking about rejecting vegetarianism btw I can foresee managing that - but even then if they start chowing down on McD I may have to say something ... or bite my tongue to ribbons.
Am I really meant to say - "that is nice dear" whatever? Cos that ain't going to happen.