This quote is from the Kalama Sutta. According to the Kalama Sutta, the Buddha talked about the Four Assurances, of which, this is the fourth. To me this was not totally different to the others, it was almost like a catch-all little area, just in case anything else is the reality - I am still purified. Whether there is a next life, whether there is not a next life, whether there are results from good and bad actions, whether there are not results from good and bad actions; the fact is that I am purified no matter what, because I know my actions that I am doing today are good actions and that I am having good results now. So it is more of catch-all little area at the end where no matter what is the case, no matter what is the ultimate reality, I am still purified.
In the case if, however, that evil results do not befall an evil doer, that still doesn't matter, because if evil results are not coming back to people doing evil, I'm not even concerned with that. I am only concerned with the fact that I want to do good, because I know from my own experience that goodness will come from it. So that's kind of how that goes.