For stronger reasons than simple modesty, certain acts involving fornication, autoeroticism, and other things people commonly “do in secret” are shameful to talk about in any public context (Ephesians 5:12), much less a church service. They may be suitable subjects for a private counseling session, or the doctor’s office, or a college biology lecture, but they are not fitting topics for a worship service where God should be glorified, Christ should be uplifted, women should be shown respect, children’s innocence should be guarded, and single people’s prurient curiosities should not unnecessarily be enflamed.

When a speaker deliberately arouses lusts that cannot possibly be righteously fulfilled in unmarried college students, or when his personal illustrations fail to guard the privacy and honor of his own wife, that is far worse than merely inappropriate. When done repeatedly and with the demeanor of an immature bad-boy, such a practice reflects a major character defect that is spiritually disqualifying. Any man who makes such things the main trademark of his style is quite simply not above reproach.

– John MacArthur