I'm just saying (I can't believe how many times I have to repeat myself on this) that we don't know much of anything about the Sheikah other than they served the royal family and fought in the war prior to ooT on the side of the Hylians. They're also called the Shadows of the Hylians and are associated with darkness/shadow magic.
We also know that they were entrusted with the Sky Book when the Oocca left the land of Hyrule, that they served as the wardens of the Shadow Temple, that they made items to see truth hidden by the Darkness.
They are called the "shadows of the Hylians" because they were ninjas that protected the Royal Family, and their association with darkness was as the wardens of the Shadow Temple. This has been made perfectly clear.
I'm not saying they hAD to be evil. I'm saying, they don't HAVE to be good either.
It's possible that the Sheikah were evil, and it's also possible that the three goddesses are in fact aliens from outer-space. If you define "possible
" as "potential speculation which we have no evidence to support
" then by all means believe what you want to believe, but that doesn't mean I have to accept your speculation if I don't think there's any real justification for it.
And this is the point that I've had to constantly repeat in this topic. All the evidence leads us to the conclusion that they were good, nothing leads us to the conclusion that they were evil. If you want to suspect the Sheikah without justification for doing so, then please stop trying to get me to agree with you, because I won't.
There's also the possibility that the Twili were never evil either. All we know is that they attempted to seize the Triforce which was an act that worked against the benefit of the people of Hyrule, and therefore it was "evil."
You seem to have forgotten a lot about Twilight Princess's storyline. The Twili's ancestors wielded powerful evil magic called the Fused Shadows, and they were shown by Lanyru to have executed their enemies with that magic. Clearly they were evil, and the greed that motivated them to seize the Triforce was just one aspect of that evil.