while you're correct they're both arbitrary scales and I've heard this argument before but still think it's a dumb argument.

Water freezes 0 water boils 100, i guess it fits the base 10 thing.

I think you feel the human 0 to 100 idea works because it's what you're used to. 0 to 40 works fine for me to intuitively know how hot or cold it is becuase it's what i grew up with too. Neither can be argued that one is more right.

although it really makes sense for the USA to just finally switch because it's long been decided by the rest of the planet this is the better way to measure things. https://media.tenor.com/SD-5sdtUX8QAAAAM/simpsons-homer.gif

0 is very cold, 100 is very hot. So 50 is perfect room temperature, right?

Nope, you still have to adjust to an arbitary selection of numbers within that range, so it's not really any more helpful than celcius if you don't have experience with the scale.

Wrong.
A middle eastern dude would tell you a 100 is fine and a northern canadian will probably tell you to stop bothering them because they are turning into a puddle.