There seem to be a lot of people missing the point on this one.
1. The airline has produced the regulations regarding what types of I.D. are acceptable.
2. The wording is clear and simple. No acceptable I.D. - no travel. There is no room for misinterpretation.
3. The handling agent works for the airline and as part of their contract they have to follow the airlines procedures and regulations.
4. It does not matter what other airlines rules are or what exceptions they make. We are talking about Ryanair not Easyjet.
I think that the check-in staff involved did exactly right.
As for anyone who thinks that company or airport issued I.D. cards or even Police warrant cards are difficult to fake think about this.
The printers and software that produce I.D. cards are not controlled items. For a couple of hundred pounds anyone can produce exact copies of credit card sized I.D. and have any name or photograph they want on them. The only real security features of these cards are contained on the magnetic strip on the back of the card, so unless all check-in desks are fitted with card readers and are connected to a computer that knows the correct codes for each person and issuing authority, there is absolutely no way that this form of I.D. can be verified.
Passports may not be impossible to forge but at least you can't buy the paper at W.H. Smiths.