system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If your stomach acid so acidic that it can melt almost anything, why do other foreign organisms and objects still pass through like nothing happen? Why do tapeworms continue to survive and other bacteria?
gpt
Lots of focus on the acidity of the stomach and too little focus on the tapeworm going on here. 

Tapeworm eggs/larvae (can't remember exactly) are inside a cyst, basically a little fatty bubble, inside of meat. When that meat is eaten, the fatty wall of the cyst is broken down in the stomach, but the tapeworm is safe inside it's bubble. It can then move into the intestine, which is a much friendlier environment for a parasite.

For other pathogens, it depends a bit. Salmonella actually is very sensitive to our stomach acid and will not survive it if you just swallowed a solution with it mixed in. However, if that bacteria can hide out in some meat you eat (fat/protein), it can survive the acidity and move on the gut to wreak havoc.