Want a simple explanation that sense restraint is an important aspect of ethical conduct, for a loved one who is not into Dhamma Could you try to formulate an answer to the above question, in line with the Pali Canon, using simple colloquial language, for someone who doesn't yet know Buddhist terminology?

I'm asking because I want to try to explain this to a loved one

For a run-of-the-mill sort of person, life would take the path of least resistance and indulgence in sense pleasures is what is long sought. It is the path of least resistance, the downward path or ‘Anusothagami’ while the traveler of this road less traveled is climbing in the opposite direction to the flow or ‘Patisothagami’. How can one get such a person to see this otherness?
Right view means understanding the four noble truths.

Right intention follows as a consequence of right view.

There are three intentions (renunciation, non-aversion or loving-kindness, and non-injury or compassion).


  And what is right resolve? Being resolved on renunciation, on freedom from ill-will, on harmlessness: This is called right resolve. (SN 45.8)


Right view gives motivation to renounce attachment (clinging to pleasure, fame, and so on ... these are usually seen as desirable but with right view you see that they lead to dukkha ... with right view you naturally choose to renounce them).

I'm not sure whether that's an important aspect of ethical conduct, though ... according to many definitions of "ethical", it's the intentions of loving-kindness and compassion, not the intention of renunciation, that motivates ethical conduct.

Still, I suspect they develop together (the factors of the eightfold path are inter-related).

It may be possible to think of examples of where someone has hurt or ignored another, either because they're busy greedily chasing a sense-pleasure or because they're suffering the consequences of misplaced attachment -- for that reason even if "ethical" is taken to mean "good to others", renunciation (to avoid attachment and suffering) is "an important aspect" (which, for example, may make it easier to follow the precepts).