How & why can sexual intentions be harmful to others? MN 19 says:


  And as I remained thus heedful, ardent, &amp; resolute, thinking imbued
  with sensuality arose in me. I discerned that 'Thinking imbued with
  sensuality has arisen in me; and that leads to my own affliction or to
  the affliction of others or to the affliction of both. It obstructs
  discernment, promotes vexation, &amp; does not lead to Nibbana.'


While I gain the impression the macho blokey male Buddhist internet scene appears to have men hoping to score jhana or Nibbana, which they imagine is a higher form of pornographic sexual orgasm, in this respect, it seems MN 19 is clear when it says sensuality is harmful to "oneself", in that sensual &amp; sexual thoughts hinder jhana &amp; Nibbana.

But why are sensual or sexual thoughts &amp; intentions harmful to "others", as stated on MN 19?
Then, as I meditated—diligent, keen, and resolute—a sensual thought arose. I understood: ‘This sensual thought has arisen in me. It leads to hurting myself, hurting others, and hurting both. It blocks wisdom, it’s on the side of anguish, and it doesn’t lead to extinguishment.’ When I reflected that it leads to hurting myself, it went away. When I reflected that it leads to hurting others, it went away. 


If one has a sensual thought about another person, one feels an attraction, a craving, a grasping. And as one acts upon that sensual thought, that other person becomes a sense-object, an object of craving. We objectify them, reducing them to mere objects of satisfaction. This is harmful to others in that it diminishes them.

And although the person to whom we are attracted may delight in our attention, they may come to crave that attention and seek it again. This is harmful to others in that we lead them astray, tempting them to seek attention.

If the person to whom we are attracted has an unattractive friend, we ignore that unattractive friend in our pursuit of the attractive friend. This is harmful to others in that we treat them with aversion.

These are only some of the ways sensual thoughts can hurt others and why they are unskillful.