If a highly advanced,well intentioned interstellar race visited earth, it is my opinion that even our most sophisticated weapons could not possibly harm them. Their defences would be stronger than anything we can possibly imagine.
I further speculate that space is absolutely teaming with life and that at least some of these species out there have advanced enough to travel
between galaxies.If this is the case than it seems logical to me that some of them have visited our own little world during our past and in all
probability are doing so today.
As far as I'm concerned the question is no longer "are we being visited by advanced aliens" but "why are they visiting earth".
I have my own theories as to why they are so interested in our development but that's all they are at the present time, theories.