The question is a bit inaccurate: the monster entry for strix lists the example strix as Neutral. So, in this case, Paizo seems to agree with the question asker. That said, the remainder of my answer assumes that the entry did make them Evil, since plenty of creatures are marked Evil for similar reasons.
Don’t try too hard to make alignment make sense. It doesn’t. There is no way for us to answer this question; it’s really a question for your DM or your whole group. Does it make sense that dwarves and gnomes can “hate” kobolds and orcs to the point that they receive combat bonuses against these races, and are “Often Lawful Good” and “Usually Neutral Good,” respectively, but strix “hate” humans to the point that they receive combat bonuses against them, and are therefore Evil? No, it does not. But that’s how the game was written: in a super-simplistic, doesn’t work if you give it any critical thought, incredibly black-and-white morality.
There are a lot of ways you can deal with this:
You can play it straight, where you are the heroes and there are monsters, and no one thinks too hard about the unfortunate implications of the system. This works well for a casual game, a dungeon crawl (which is, after all, what the system was originally designed for), and so on.
You can ignore it entirely. In this case, your character’s morals are what they are, and alignment doesn’t have mechanical weight. Requires a bit of houseruling for things like detect evil and blasphemy, though. Well-suited both for casual games (where you don’t worry about things like morality), as well as for serious games where questions of morality are far too complex to fit into the nine bins that are available.
You can consider “[Good]” as distinct from “good” – the former being an alignment, while the latter is actually a statement of morality. “[Good]” creatures may tend towards “good” acts, but ultimately being “[Good]” is more about “[Good]” acts than it is about “good” acts. This works pretty well because it doesn’t require houseruling any mechanics, you just have determine which sides have which alignments.
But all of these require group input, because you cannot decide them for yourself; these fundamentally are questions of the tone of the game.