@PostItEase They're not talking about hurting it by making it fall. They're saying trash (yukkuris) belong in the trash can and that it would be funny if it was positioned so that when the babies are born, they fall into the trash. Personally I was thinking that it would be funny if it was offset so that when she steps out of the box in the morning she falls into the trash can and hopefully the stalk gets caught on the rim and snaps off.
I think anon's move is brilliant in so many ways. Either Reimu wakes up, hops out and hurts and injures herself so she can't go forage (slow death), or she hops out, falls over and snaps off the stalk. Or the babies get born and fall to their deaths, or the babies get born, mommy leads them out and all the babies flop to their deaths.
I can't tell whether the entire Reimu, including stalk, is in the box or not because of the flat perspective. This means there's three possibilities I can see:
a) A misguided helpful anon lifted the box to keep it safe from intruders, failing to realize that only the Mom could possibly survive a fall that far, and depending on if the garbage can is to scale, possibly not even she could.
b) A malicious anon lifted the box so the babies wouldn't be able to get out, and the mother might not be able to either... but there's no immediate threat.
c) A malicious anon lifted the box so the babies would fall too far to the ground and die.
I think "a" is the most amusing, having seen and heard of too many clueless people who try to help animals in ways that only end up hurting them... but given the yukkuri fan community, "b" or "c" was probably what was intended.