Why was a measure for measure dealing a length with immorality issues and where were they potraid?

Measure for Measure is a play pretty much obsessed with death. I guess mortality or immortality are closely linked sex an marriage. Sometimes the characters are comic about life and death; some times thety are more serious.

Better it were a brother died at once,

Than that a sister, by redeeming him,

Should die for ever. (2.4.14)

Here Isabella insists that her chastity is much more valuable than her brother's life, because having sex with Angelo would condemn her to an eternal death (hell). Is she right?

I will encounter darkness as a bride,

And hug it in mine arms.(3.1.9)

Once again, Claudio associates sex (and marriage) with death. (If we didn't know better, we might think we were reading Romeo and Juliet when we encounter this passage. In that play, sex and death go hand and hand for the "star-crossed" lovers.) Here, Claudio compares dying to a woman losing her virginity on her wedding night, which turns death into a kind of erotic state. This doesn't surprise us much, especially given the fact that, in Elizabethan slang, "to die" means to have an orgasm. The comparison works.

These are a few excerpts I took from the source link below.