How sweet and lovely dost thou make the shame
Which, like a canker in the fragrant rose,
Doth spot the beauty of thy budding name!
O! in what sweets dost thou thy sins enclose.
That tongue that tells the story of thy days,
Making lascivious comments on thy sport,
Cannot dispraise, but in a kind of praise;
Line four begins with an  exclamatory  “O!”, suggesting high emotion. The poet doesn’t condemn the young man but instead seems almost joyful that the youth’s beauty hides vice: “O! in what sweets dost thou thy sins enclose!” Here, “sweets” is used in the archaic sense of sweet nature or beautiful appearance.
Sonnet 95