Maybe it is just rumor but I heard that the Bitcoin network is already the world's largest computer network by an incredibly large margin. Is that just a lot of bunk? Because if what seems to be an excessive amount of capacity is not on the table after months of debate about blocksize to the point of nausea then why? How much capacity is just the right amount of security?
Actually the internet is the worlds largest computer network. What is "an excessive amount of capacity"? Capacity for what? Block size is not the Bitcoin network but rather the blockchain itself, which is different from the network. The network has immense capacity, just like the internet. Loads of data passes through the network, but the blockchain, that is a different matter, which is separate from the network.
I've heard (don't know if it is reliable) that the Bitcoin network has the computing power of the top 500 supercomputers combined. Is that true or a bunch of horsecrap? if not true, let's get an accurate number. If true then it would seem talk about loss of security is not accurate.
It is not comparable. Supercomputers are almost like general application computers. They can do a lot of stuff, they are application specific like most mining hardware is. Sure the hash power is probably capable of producing SHA256d hashes faster than any supercomputer, but when it comes to doing other stuff, especially for benchmarks, the network can do squat. It is not a fair comparison, in fact, it is essentially a comparison of apples to oranges, they are two different things.
As for a loss of security, while the loss of security at this time may be small, we shouldn't do anything which can result in any loss of security. However small the loss is, if we can avoid it, we should.