Purposely sending signals into space is akin to a 5 year old kid calling random people, telling them he is home alone and what his address is.
Yea, I've heard Stephen Hawking among other scientists say that things likely wouldn't go so well with the aliens despite the fact many people would like to believe they would be benevolent.
I think the comparison he made was how did it work out for the Native Americans in North Amercia when the Europeans arrived. Not great.
One possibility - if Aliens exist - is that first contact with a species at our level of development is not without precedent for a civilization as advanced as the ones we envision. Consequently, the analogy Professor Hawking draws is a scenario extra terrestrials may well be aware of. It could also explain why - assuming their existence and awareness of ours - they don't land on the White House lawn and holla "welcome to the neighborhood!" or rise out of the ocean in a display of wanton spectacle.
You don't tell your kids outright Santa isn't real; you let them figure it out or coax them round to that conclusion when the time's right. Maybe the best approach is a very gradual introduction; what we produce in our entertainment has certainly acclimatized us to the concept
of alien civilizations.
As for Aliens that arrived that were hostile. Well, we're still here. I know that's not an argument for there are no hostile aliens. But consider we've already extrapolated where our technology is taking us is terms of liberating us from competing for resources. If you've got a civilization that has persisted for thousands of years minus the infirmities and resource restraints we face, then - unless we were perceived as a threat significant enough to commit resources to our extermination - I can't think why hostile would be the default position of extra terrestrials.
I've often considered the possibility Aliens sufficiently advanced might not partition reality up as we do. What I mean to say is they may view the Universe as 'home', not a particular planet or point of origin. We could be children playing in a sandbox that they're concerned about.