Aer Lingus tried to expand into Gatwick and failed, but neverless, because they failed this makes them good, but because Ryanair succeeded this makes them bad.
You have completely misinterpreted what people have said. Nowhere has it been said that Ryanair's success outside of Ireland is a bad thing, it's very clear that almost everyone respects Ryanair for its success and the fact a small Irish airline is now one of the worlds largest.
The discussion of Ryanair and its Irish operations cropped up when a comparison with Aer Lingus was made with regard to the take over attempt and the profitability of the two carriers. While Aer Lingus is profitable purely because of its core Irish operation, Ryanair is not and its profits come from across the European network. This means a fair comparison of both airlines profitability within the Irish market (the market that the take over mainly covers) is difficult as Ryanair does not divulge in details of which part of the network makes the most/least money.