Each advocate for each Doctrine personally should be able to know that reason for what they believe. Additionally each should recognize that those who hold opposing views also fully believe that their position is supported and reinforced by Scripture.
Brilliant point, captain obvious. Yes, you are all "cafeteria Christians." You take what you like and throw out the rest. Heck, Bill is probably the most glaring example of a Cafeteria Christian.
The atheists are the only ones who have it right: We call BS on all of it.
Using your analogy, Bill and his FRANs would go into the cafeteria, get some broccoli and when they came to the green beans would ask why they were serving broccoli again. He would certainly refuse any unleavened bread products, and suspect the owners of being Catholic. Then he would take his fork, say it is a spoon, and try to eat soup with it.
Bill would go on to study the menu to the point of knowing every item listed and every ingredient, and if he didn't understand any of the French titles like "soup du jour" he would have it transliterated until he understood it to be "beans and wieners". Using various menu items he would then project when the cafeteria actually opened that day. If he happened to see that tonight's special was a "bottomless bowl of salad", he would expect the bowel it was served in to be literally bottomless, and when he actually saw the bowel would proudly and assuredly claim that the bowel did indeed have no bottom.
As Bill and his FRANs pay on the way out, Bill would accuse the cashier of being a plain old vanilla cashier, **** her to hell, and wish her a blessed day.