I think that pass is right, but it may not be the winning action. I just believe it rates to be right more often than not.
Partner is not going to act in direct seat over 3♠ facing a passed hand on a lot of hands where we should be bidding or penalizing them. But, IMO, there are even more hands where acting here is going to lead to a worse result than 3♠ passed out.
There is no reason to believe that the 3♠ call is anything but a normal action on LHO's hand, so unless I have some good reason to act, I am going to take the action that I believe is normal and pass out 3♠.