Discounting stories in the Mirror and Mail is a totally reasonable tactic.
UK papers do not have fact checkers like US publications. UK papers very carefully report what someone says, even if most people agree that person is a wingnut and talking nonsense.
Looking at the UK tabloid newspapers we see some deeply nasty methods where blatant lies are told and nonsense peddled.
If the Daily Mail told me that grass is green I'd have to go out and check.