Rambam - Sefer HaMitzvos: Positive Mitzvah 105: Positive Mitzvah 105

Positive Mitzvah 105: Impurity caused by Discharge
Leviticus 15:16 "When a man discharges..."

The impurity of Shichvat Zerah may befall a man.

Rabbi Akiva taught to love for your fellow man to the point of giving your life for him. Yet his students died of a plague because they did not treat each other with respect. How could it be? There are times when love can kill. There are times when you love someone so much, you cannot allow him to breath. He must do things the way you understand is best for him -- because you cannot bear that one you love so much should be in any way distant from the truth as you know it.
"After all," you imagine, "I must do for him what I would have done for myself!" But true love makes room for the one you love. As Hillel the Elder put it, "That which is hateful to you, do not do to your fellow." True love is best expressed not in what you do and what you say, but in what you do not do, and what you do not say.

From: Bringing Heaven Down to Earth by Tzvi Freeman - tzvif@aol.com