I think it's entirely legitimate to ask intelligent questions about how human factors are affected by short turnaround times.
Very short turnaround times are a comparatively new way of operating an airline. From a "conservative" safety standpoint, anything radically new must be assumed to be potentially unsafe until proven otherwise.
What is NOT ok, in my humble opinion, is to make blanket assumptions and sweeping generalizations regarding safety based on a single incident (and it's even less helpful when such assumptions are intermingled with a general animosity towards everything Ryanair). Memmingen wasn't the first, and probably won't be the last such incident in Ryanairs history either. It's human to make mistakes. Cork 2006 (
Serious Incident: B737-800, EI-DCT, Cork Airport, 4 June 2006: Report No 2007-002 | AAIU.ie ) comes to my mind, and some other similar incidents.
Ryanair landed safely 3.34 million times between 1992 and 2011, without a single fatal accident. That's a good safety record. And a lot of flights. Unsurprisingly, there will be some ("serious") incidents, like Memmingen and Cork.
Ryanair has all the FOQA data, in near real-time, and I trust they use it for all it's worth.