I don't think it is necessarily evil to use the tadpole powers. There are a number of situations where using them avoids bloodshed and not using them results in death.
There's nowhere where you can use the tadpole to resolve things non-violently that you can't also solve without using it.
It may certainly be understandable that a character reaches for this as an option, because they're scared, or focused on surviving and see it as their best survival option, etc., - but mentally dominating another sentient creature into obeying you, when they are not inclined to, and robbing them of their free will in the matter is definitely an evil action; that's not to say that it should be restricted from good players, or that good players should feel like they can't, or must not, and one or two instances of doing this, in desperation, isn't going to force anyone's alignment necessarily... but using it in the way that we do is definitely evil.
Using it to read someone else's thoughts, on the other hand, is more negotiable - that's no different from detect thoughts, really, and while it's an invasion of privacy, definitely, it's not on the same level as violating someone's free will or mentally compelling them.
My characters generally don't touch the tadpole options at all - they view it as an invasion, and they also don't want to agitate the thing that may destroy them body and soul, just out of pragmatism. Some of my characters do, but most don't. IT will be a poorly designed game if abstaining from this, when there's really no temptation or seduction at all, just cuts you out of content and leaves nothing in its place.
