taking a stand

What is it about taking a stand or making a statement that results in people madly searching for inconsistencies?

I do not eat pork, but people often ask me why I do not have bacon with my brunch. After my explanation, some go further and go through a list of foods to challenge me, "yeah, but do you eat ribs? Do you eat hot dogs?"

A friend of mine is kosher style at home. He has his own flexible rules which are certainly his own business, but that drives people crazy. They prod, they debate... why?

I am boycotting products from France because of their recent bigot anti-semitic behavior. They served Evian at a meeting I was at yesterday and I drank it. I did not buy it, but how quickly do you think my colleague pointed that out?

Is it that people wish they too had standards? Do they wish they had something to care about? I don't get it.