hpurey: losses don't show up on your profile page so nothing to delete.
I've never seen that a player can fumble at his profile or stats. The activity log is biased on the positive side - it shows only wins, as stated before.
The stats tab, OTOH, shows wins and losses in the Matchplay section. There I've seen a minority of match losses, and an A/S balance which was slightly negative.
Of course, incomplete matches don't show anywhere but in the completion tag.