How to eat, or not?

It is a challenging world we live in, at least dietarily, especially when feeding company.  I had a friend who had one side of the family that was vegan (no eggs, milk, or meat) and the other side was gluten free (no flour type products) and they were all at her house at the same time!  Some people have a medical necessity to avoid certain foods (allergies, sensitivities, celiac disease, etc.) while others have basically jumped on the idea as a fad or alternative religion.  Is gluten free still all the rage or have we moved on to paleo or something else?  Remember the atkins diet?  Even the scientific opinion on the subject seems to shift sporadically.  Eggs are either bane or blessing depending on the year.  Salt and cholesterol and red meat were going to kill us back in the '90's but now it is okay; coffee and red wine are also either miracle or poison, depending on the most recent study.  So how do you cook for people at all in this day and age when everyone has a medical necessity or a strong preference?  Especially when many who have elected to eat a certain way get highly offended when you don't bow to their wishes?  Why is it people who have a medical reason for their diet are so much more accommodating than those who choose to eat a certain way?  I've never been preached at by a celiac patient that gluten is evil, but I've heard plenty of sermons on why I need to eat organic or go vegan or avoid red number 5.

Even the food labels have gone bananas.  They no longer say what's in the product (well they do, in teenie tiny letters) but the big bold lettering goes to such proclamations as fat free (jelly beans, 100% sugar), gluten free (salt), no antibiotics (poultry, but you get in big trouble if you sell tainted meat so I'm not sure what the point is), natural flavoring (soda, definitely a healthy alternative), no preservatives (this really irked me, granola bars are supposed to have a long shelf life!)…you get the idea.  No wonder people are confused by what to eat and how to cook.  But a little common sense will go a long way in this as in all else.  Eat what you like, a wide variety and all things in moderation.  There is no magic diet that will let you live to 100 regardless nor will eating bacon (or whatever) once in a while kill you.  On the other hand, worrying about it too much may just give you an ulcer.  Also, if you are enthusiastic about your new diet, that's fabulous but please don't beat us nonbelievers over the head as dolts and evil doers, we're living as we think is best, just as you are.