It was said in court by the prosecution.
Search Google News for "Darren Osborne " "Rochdale" "three girls"
Plenty of hits.
Did you not think of that Greg?

Example,
"Finsbury Park terror suspect 'developed hatred of Muslims after watching hit BBC grooming drama Three Girls'"
http://www.mirror.co.uk/news/uk-news/finsbury-park-terror-suspect-developed-10680150

I am away for a while.