Agreed, unless we haven't gotten a hold of all the physics necessary for trips on that scale. That said, I do think it's overly pessimistic to think that aliens would mistreat us as a matter of course - obviously we've done a lot of that to each other in the past, but I'd like to think that most modern societies (say, Norway, to pick a random example) wouldn't just casually enslave and kill a new tribe. We're at a point in our history where even the idea of colonizing is anathema (not that there isn't plenty of fallout from before that was true...). So I don't have a hard time imagining a species that's thousands, hundreds of thousands, or even millions of years ahead of us would have a very different take on interacting with other sentient beings (assuming we make that cut for them).