That covers the first sentence. How does it connect to the second one? So far, you've described how you would expect bats to carry very few diseases, because diseases that found themselves inside a bat would be killed by the temperature fluctuations. It does not appear to follow that bats should be hosting a lot of diseases at any given time.
You've made an interesting counterargument that I've never come across before. I'm purely speculating here, but maybe the diseases in question (rabies, nipah) are otherwise so deadly that they'd normally just kill the host, but in bats, they linger on. All that to say, that bats aren't necessarily hosting more diseases relative to other animals, but they harbor diseases at the more lethal end of the virulence to transmission tradeoff spectrum.
