Is there a scenario where a user has the CORRECT seed entered and Electrum would present a grey'd out button because his software/computer is corrupted?
software being corrupted: i doubt it, even if you download a malicious software from another place other than electrum.org the way seed works is not going to be different.
even if the integrity of the downloaded file is damaged, then again i doubt it can happen.
computer corrupted: again i doubt it, because Electrum is not using any external resources like .net framework for some other applications or something similar. it is all in the code and has nothing to do with your computer for checking the correctness of seed!
So you seem to be seeing that a grey'd out button is always because the seed entered does not mathematically resolve in Electrum therefore it "grey's out"?
yes that is always the case.
i wouldn't say your solution is a "wild goose chase" but it is a solution for paranoid people and as the last resort!
download TAILS, which has Electrum in the build,
are you sure it has Electrum built in?
also why TAILS, you can do it with almost all other linux distros and i prefer downloading Electrum myself, checking the signature and installing it myself!
all of these can be done on a virtual machine.
TAILS will mount in RAM
to my knowledge this is wrong.
TAILS runs from the medium you are booting up (DVD, USB disk, External HDD,...)
download a fresh copy. Verify the download and install it again. That is a couple of minutes at most.
as long as you can do this, going to the trouble of downloading TAILS, checking your seed,... is not recommended.