When we meet a civilization from another planet, it will almost certainly be much more advanced than ours just because ours is so new. The question here is will they treat us the way we treat less advanced and weaker civilizations? If so, we should beware. But how likely is that?
Our European-grown global civilization, descended from the great Roman slave empire, has a quite extraordinary record of discovering new (to us) civilizations around the globe and conquering, plundering and consuming or destroying them. There have been voices denouncing this practice for a long time, voices of the victims and of radical critics from Padre Las Casas to Mark Twain, but It's only in the past century that any serious effort has been made by governments to restrain or reform our predatory practices. So it's only natural that we imagine this is what others would do to us.
There have been many science fiction stories and films, starting with HG Wells' classic War of the Worlds, where aliens discover and trying to conquer or destroy us. One awesome recent science fiction film, Avatar, turned the story on its head and told of the plundering of a distant planet inhabited by intelligent beings - by us! But ultimately all these stories are not about alien life, about which we know nothing. They are about ourselves. Only a few, like ET, Close Encounters and Carl Sagan's Contact, depict aliens as benign.
So how likely is it, really, that an alien civilization would be dangerous to us? I think it's unlikely.
Any civilization that reaches our level of development must either bring its predatory phase to a close or destroy itself. That is the moment we are in. They will have survived and gone beyond it.
Second, the distances are so impossible in terms of a human life-span that the only thing we really have that they could want is our story.
The huge benefit of contact to us would be hope, hope that we too could survive our predatory phase, that humanity could have a future.