I agree, so long as the couple goes into it with both agreeing that it is what they want to do and one isn't dragging a reluctant partner into it.
In our poly family there is plenty of opportunity for conflict that has nothing to do with sex. (Actually, the sex is a thing that helps smooth out the disagreements, and not that the two fighting suddenly become lovey dovey and make love. It's that we have others to turn to that give us solace, love, a dose of reason, and an orgasm to better the mood. Then all is forgotten.) We are fortunate that we all have the right temperament to deal with it and love one another enough to compromise, and therefore, have thrived as a family and individually.
When it all started and it was just my husband, my boyfriend and me, I was concerned that there would be times when I wouldn't give hubby enough intimate attention, so I was always sensitive to whenever he wanted to pull my pants down. Now it's the opposite: with three women and two men in the family, the guys can't keep up so we women share a boyfriend. We are all sensitive to the others sexual needs.