The Queens Park Rangers manager, Mark Hughes, has warned that football may never be rid of racism as police launched another investigation into allegations of racist abuse, this time at Sunday's Tyne-Wear derby between Sunderland and Newcastle at the Stadium of Light.

Police made 15 arrests related to the game and said the majority of the 47,456 crowd had been well behaved, but again the spectre of racism raised its head. "There was one report of racist language having been used by a supporter in one area of the stadium – inquiries into this report are ongoing," a Northumbria police spokesman said.

Hughes's comments came after several of his players opted not to wear T-shirts supporting Kick It Out, the anti-racism football body, during the warm-up for their game against Everton at Loftus Road. Anton Ferdinand, the target of racist abuse from John Terry when playing for Rangers against Chelsea last season, was among those who joined the protest, while several Everton players, including Victor Anichebe and Sylvain Distin, did the same.

"It's a personal thing but my personal view is that any campaign that focuses on trying to take racism out of sport and football is a good thing and we should try to support it," said Hughes. "Everyone will have a view about whether or not enough is being done. Sometimes someone will take a personal view that what's being done is not enough but you'll never get rid of it totally. I don't think so. It's very, very difficult. There'll always be some idiot who feels that it's something they want to do."

The QPR manager suggested that Kick It Out itself was not the target for the players' disquiet. "I think the point is being made that they want more to be done," he said. "I'm sure because of their strength of feeling that people within these organisations will look at themselves and question themselves and maybe that's a good thing and maybe that's why the guys feel strongly enough to do that."

Neither Hughes nor his opposite number, David Moyes, will be sanctioning their players as a result. "It's too big a subject for my opinion to matter that much," said Moyes. "But I did speak to the players – I did give them the opportunity [to air their views]. It was up to them to decide what they wanted to do and how they felt.

"I spoke to them and told them how I felt. I understand their points of view. I'm totally supportive of my players in what they choose to do but I actually think the Kick It Out campaign has been a great success."