Simple answer? Don't.
And it has already come down to you in the Book that when you hear the verses of Allah [recited], they are denied [by them] and ridiculed; so do not sit with them until they enter into another conversation. Indeed, you would then be like them. Indeed Allah will gather the hypocrites and disbelievers in Hell all together
And when you see those who engage in [offensive] discourse concerning Our verses, then turn away from them until they enter into another conversion. And if Satan should cause you to forget, then do not remain after the reminder with the wrongdoing people.
Why are you letting disbelievers tell you what is or is not a good example, instead of putting your faith in Allah and His messenger? Why are you letting yourself be drawn into arguments on sociology and sexual health when you are not knowledgeable in either of those fields?
Instead of arguing without knowledge about topics they understand better than you do, which is exactly what they want you to do, you should just be leaving them to their disbelief; if you want to strengthen yourself in the face of such questions in the future, studying the relevant fields (be they religion or science) with the guidance of a knowledgeable teacher whose goal is spreading knowledge will fare you much better than letting these disbelievers teach it to you, when their goal is simply to spread their own disbelief.