I think there's at least some reason to be a little more optimistic. Aliens technologically capable of visiting us are likely to have progressed through much of the same social development we have, and more (assuming that the pattern that has held for our species is common, which seems reasonable). We are still doing terrible things to each other, but not as often as we used to; I think it's likely that aliens would be kinder than we are. Then again, it's also possible that they might accidentally harm us - even a gentle child can crush an ant without meaning to...