I do not think compassion ever ends in the teachings of Buddhism. However, compassion can be expressed in various ways. It is also said that true compassion is expressed by wrath. Although it is initially difficult to understand how someone being harsh with us is a form of compassion but it does make sense once we look deeper. Due to our own attachments to our ignorance, ego and anger, we can sometimes become stuck onto our old ways that does not serve us. Therefore, under such circumstance, wrathful methods that is practiced with wisdom, compassion and skillfulness may be needed to cause a required shift in our minds. However, I do agree with Klein that one must be cautious with the use of wrathful means because if our intention is unclear, it is possible to cause negative outcome.
As mentioned by Michaela, what do we mean when we define a religion to be passive? If non-passive means aggressive, then I would say “Yes, Buddhism is a passive religion”. However, if non-passive means the proactive approach to living your life, I would say “No, Buddhism is a vibrantly creative and proactive religion.” From my understanding of Buddhism, our fate and destiny is completely within our control. The law of karma is not what many people blatantly claim: “Oh, such is my karma, I just need to accept.” On the contrary, with every choice and action of body, speech and mind we get to “manage” our karma in a manner that empowers us to progress towards deeper learning realizations, attainments and eventually enlightenment. Of course this sounds simpler that it is to do, which gives great dynamics and challenge to our minds that is contrary to passiveness perceived of Buddhism.
Thus, I would like to conclude my view that compassion never ends although the methods to practice and convey it may be varied. Additionally, Buddhism is one of the most powerful, dynamic and mind-blowing teaching and way of living that I know of.