There are many actions you can take on your friends’ status updates on Facebook.
The first action is inaction. If you feel indifferent, or lazy, or if the “friend” is just an “acquaintance”, you can do nothing. You might feel like a voyeur (or stalker-lite) for peeking into someone’s life without being an active part of it, but that’s what social networks are all about (e-stalking). This is also about as passive as you can get on facebook.
If you feel strongly for or against the status, or if you follow this flowchart, you may choose to post a comment. This is about as aggressive as you can get in a virtual environment short of throwing punches in super poke.
If you feel less strong FOR the status, but would still want to alert the poster so that they know that you know that they’re up to something, then you can “like” their status. This is a passive-aggressive “like”.
If you feel weakly AGAINST the status, however, all you can do is “hide” their status (but hide actually has a different semantic meaning both in the term itself, and the actions that facebook takes once you hide something). The original poster will never know that you hid their status, and any passive-aggresiveness that only one person is aware of is no aggressiveness at all.
Hence the asymmetry.