I can't help observing that the vast majority of people who aren't worried about the demise of guards are youngish to middle aged males, more than capable of looking after themselves in a threatening situation on board. Ask any pensioner or lone travelling female what they think, and the consensus is always that we need a second authorised member of staff on every train, not just those after 8:00 pm.
The emphasis on "safety", in this specific area, is as much personal safety while travelling as it is to do with door opening and closing operations. I understand there is a widespread drugs culture in the Merseyside area, and sadly some of the less amenable sectors of society will use the trains at all times of day. (Is that diplomatic enough?)