Firstly - it's important to remember we only know the facts as reported by the media - (which must always be treated with a pinch of salt!).
Although I agree clearly morally wrong to refuse entry to military personnel, the hotel isn't actually breaking any laws by turning away a potential client. Many hotels have such policies, eg, no stag do's, no groups of footballers / football supporters, so on and so forth - and sometimes this includes no squaddies - purely from the establishments past bad experiences. While this may seem (and be) unfair to the majority of good people, the sad fact is sometimes such a blanket possibility can be necessary in order to safeguard their premises and other customers.
I also wonder why he showed a military ID card to the hotel staff, instead of a driving licence or passport? I guess military (unlike police)ID cards are Home Office approved forms of Identification so nothing wrong with using it in that respect - but sometimes holders of such ID's try and use them for personal gain, eg discounts which does, on occasion, backfire.
Without knowing the facts from the horses mouth so to speak, I'm not going to form a solid opinion based on media coverage alone, so I'll keep an open mind