Abstractions are frequently used in a court of law - e.g. guilty beyond all reasonable doubt, or 'do you think, in all likelihood, that the defendant is guilty' etc.

But just because emotions are abstract and so can't be measured in a court of law, doesn't mean you can say or do whatever you like - all humans have an emotional intelligience of sorts - you can tailor your actions according to how you perceive people acting - just because emotions are subjective doesn't mean you should treat others however you like, without thought for other people - I suppose, basically, you should treat people as you expect to be treated - people might accuse of acting improperly, but you are on safe ground, because you consider you acted properly at the time .