I wouldn't call it playing dirty however, I would suspect that both the airports concerned and the two airlines were just scrapping to try and gain some advantage over the other. One thing is for sure, I think that we are going to have a big face off between Wizz and Ryanair in the coming months as it really is now starting to feel like the beginning of a war.
Thing is that FR has the cash for a war but Wizzair doesn't and will bleed very quickly. Its financial affairs have often been commented on and there are enough reports available which gives the detail.
Wizzair needs to pick its fights that it can win.