If a friend touches one’s penis, then touches clothes and the body, does this constitute a defilement that necessitates ghusl, and is it forbidden to give in to obsessive whispers?

Do not rule that the hand becomes impure by placing it on the aforementioned organ, nor do clothes become impure by being touched by that hand. The default state of things is purity, and nothing is ruled impure unless one is certain that impurity has touched it. Yielding to obsessive doubts (waswasah) may be unlawful if it is possible to stop them, as they can lead to neglecting obligatory duties. It is incumbent upon the one afflicted with waswasah to cut off the source of these doubts and to pay no attention to skepticism, for it is an act of Satan.