Is it permissible to mock and ridicule girls and homosexuals online with the intention of teaching them a lesson in their lives, knowing that the one doing so is a believing young man who fulfills all of God's obligations?

If you can communicate with those who commit sins, you must advise them and denounce their actions using legitimate means, citing the Prophet's (PBUH) sayings: "Religion is advice" and "Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart." The advice should be given kindly and gently, like treating the sick, in accordance with His (the Almighty's) saying: "Invite to the way of your Lord with wisdom and good instruction, and argue with them in a way that is best," and the Prophet's (PBUH) saying: "Indeed, gentleness is not in anything except that it adorns it." Enjoining good should be done with good, and forbidding evil should be done without evil, while avoiding sterile bickering and arguments that lead to aversion and waste of time.