how to convey it matters

Manuel and I, as we traveled back to the city, had a mano a mano talk. I tried to correct one key point that he seemed to be unclear about. That if he changed his plans during a CAO visit, that he should, out of courtesy—principally for other members—let the organisers, and in particular the bookings person, know. He said that Tony had told him it didn't matter. I said that I thought Tony meant that he didn't want Manuel to worry about a mistake this time, but that in the future it would be in fact important. He had booked space for three people including himself and consequently it was noted that the CAO bed spaces were "full." When his two guests changed their plans and he did not inform us of the cancellation, it may have prevented members from booking, thinking they'd have to sleep outside. He "held" or "blocked" space. When we might have received more members for such a nice weekend. In the end, I felt stymied. I don't think I was able to convey my thoughts correctly. Manuel seemed very upset and unreceptive. And I realised suddenly that we were both equally stubborn.