I usually do one full wash on 90 degrees every month. Sometimes it's my towels, flannels, bath mat etc, other times it's the kitchen towels, cleaning cloths etc.
This morning, a friend whose washing machine has broken (filled with water) dropped off the towels that were in there when it broke. My flatmate said he hoped I wasn't going to wash them on 90 because it's inefficient and unnecessary. I said I was because it's better for the machine ("bollocks") because it dissolves any powder or conditioner left in the pipes ("it'll dissolve anyway") and kills any bacteria ("the powder will do that"). I said I was, because they've been left damp and smell a bit grim.
I've just been into the kitchen and he's put them on a daily quick wash at 40, and I've no idea what detergent he's used (I was going to put vinegar in because they smell musty and damp).
AIBU to think he's being an arse making his point, and doing the odd wash at 90 (especially to help a friend) really isn't a huge issue?