Question

What is Friar Laurence saying?

For nought so vile that on the earth doth live
But to the earth some special good doth give,
Nor aught so good but strain'd from that fair use
Revolts from true birth, stumbling on abuse:
Virtue itself turns vice, being misapplied,
And vice sometime's by action dignified (II. 3. 17-22).

Everything is good if you look at it right.
Everything is good if correctly used.
Everything good turns bad.
To get good, you must do bad.