Well not focussing on a set of rules does make very thing a bit harder and the words of Jesus can be jarring but it does help us from falling into legalism.
Well, I'm sure that's a devilish trap worth avoiding. But it still doesn't help us get a grip on this area of moral
realism you are talking about (this sort of thing of course has its own thread). From your point of view, it's supposedly somewhere in the scriptures, and there is a sort of feel of 'goodness' about some of the statements of Christ and St Paul - and also a lot which we might be happy to dismiss. Not because the bar is being set too high, but because we realise that we live in different times, and have learned that the commands of Jesus (insofar as they were accurately reported) and the injunctions of St Paul were extremely
temporal. They both, after all, tailored their ideas according to the conviction that the world was shortly coming to an end.
As for maintaining some vague idea of 'love' as a guiding principle (Jesus and Paul both strong on this), this has often been put into practice according to the adage "Love the sinner, but hate the sin". The latter part of that phrase brings you right back into the niceties of legalism.