I'm a retired lifetime railway employee (safety manager), and a severely disabled person who travels around Europe a lot by train.
The most important fact is missing from that article, and it's whether either passenger booked help in advance.
Anyone can request help for rail travel, but if someone not disabled or elderly, travelling with a pram had wanted to reserve a space for the pram, PassengerAssist would have told them to call Customer Services, who would have told them that a pram or buggy should be foldable, put in the luggage compartment, and the child should travel with the adult. It's a safety issue, safety takes priority at all times, passenger comfort comes second. Passengers have a responsibility here, prams are dangerous even if braked. The only safe way of carrying a pram on a train safely, is secured with chains or lashing tape as used for aircraft loads, in a goods carriage. When did you last see a goods carriage at the back of a passenger train? Not for several decades.
For a person travelling in their own wheelchair calling PassengerAssist, the train company would provide a ramp to board and leave the train and reserved a wheelchair space with reservation card on it with the passenger's name and the departure and arrival stations.
The train and station staff (train company or Network Rail depending on the station) get a daily updated list of special needs travellers they need to look out for and the help needed. Help booked for same day travel is telephoned through to those who need to know, confirmed by email.
PassengerAssist serve disabled and older passengers; they are able to book priority seats and wheelchair spaces on trains. Customer Services serves everyone else; they can't book priority seats or wheelchair spaces.
The guard should be on a disciplinary charge, the train company should look at their staff training. I suspect this is a one off, it still shouldn't happen. The guard would have been alcohol-tested at the first opportunity and taken off duty until after an enquiry and retraining if necessary. Great Western Railway have had to change plans to update their rolling stock because of the expensive failure of the Great Western Main Line electrification project. They're running some of the oldest, least disabled-friendly trains on the railway – many from 1976 on the main line services to my knowledge. New trains are planned to have better facilities for disabled people.
The railway needs to be renationalised completely, vested in a company without shareholders, a for-profit body with all profits put back into the railway, run at arm's length from government, by experienced railway managers, so that everyone can talk to everyone else. Bring back the old Rules of the Route system to manage repair and maintenance planning so everyone knows what everyone else is doing, nationally..