Sinning, as Jesus and the church say, is good. Turn or burn Christians.

[Greatest I am]

We wouldn't call necessary evil necessary evil if it were good.  The notion of a sum good (or a sum evil) is a credible position..but, as the name implies, it works by tallying up specific goods and evils, not by declaring all constituent parts goods on account of the sum.  Incoherent aside from a frank acknowledgement of the evil side of the ledger.

I agree with you that life will ignore morals to live - I think that whatever compels us to do that is a better candidate for sin than sex or competition.  Life being willing to do the wrong thing doesn't make the thing less wrong, and doesn't even help to build the case of a necessary evil.  Life will do the wrong thing to live even when it isn't necessary.

That, right there, is the essence of sin.  The will to do wrong even when you could do right.  Even when doing wrong harms you.

I call necessary evil, necessary evil, because that is what it is. If it were good, I would name it that, which I do, in the context of extinction being the other choice. Do you offer some other word?

As to your last.

Give a proof of concept with a real life example. We tend not to hurt ourselves.

Regards
DL