Whoever has doubts is condemned if they eat,
because their eating is not from faith;
and everything that does not come from faith is sin.
The old adage, "When in doubt, don't.," is solidified in this scripture. This chapter gives both the vegetarian and the carnivore permission to eat what they want if they are convinced it is good for them to do so. The matter remains between them and God and we have nothing to do with it. I stand in judgment too many times of large people who chow down and vegetarians who refuse good meat. I'm sinning when I do so.
I know what is good for me to eat and yet, in the confines of my own home, I eat it anyway. I need to listen to my conscience, a.k.a. the Holy Spirit, who says, "You shouldn't have that." I argue and say, "One won't hurt," and I eat it anyway. I need to realize that God knows what is best for my body and tries to tell me what to eat, drink, watch, listen, etc.
Now, why don't I do what He says?
Yet, again, I'm sinning and I know better.