I think it depends on how we find the life.
I believe in ET life, obviously, but I feel like extremely evolved life is probably quite uncommon. So I think if WE found a planet with ET life, I feel like it'd be more likely to be full of some kind of more primitive creatures. And I don't think that's human ego speaking, I just genuinely believe that statistically speaking less-evolved life forms (eg. Animals, microorganisms) must be more common than more-evolved life forms. I mean think about it, given the amount of planets we believe are entirely dead, it must be likely that much of other life is less evolved... Right? For this reason, I feel like if we found other life, it'd probably be lower evolved creatures and thus likely relatively safe...?
On the other hand, now that I think about it, isn't our star (and thus earth) a relatively young planet in the universal timeline...? I guess actually other planets have had much more time to evolve so... I guess actually it's pretty likely other planets have creatures more evolved than us?
Either way, I think an ET finding OUR planet would be bad. Like @ohml
said, I'm certain an ET that is able to travel that far across space, and is that advanced, would probably not be specifically impressed or empathic to us.
Wow. I never thought about that before though. Earth is so young in the universal timeline. Other planets have had billions of years longer to evolve...... What would another few billions of years of evolution even look like?