Oh Miguel! 🙂 I reckon this subject will be ok here although I too have seen a fair amount of insults going back and forth on various social networks.
I have two cats. The reason I got them was that when we moved into our country house it was infested (and I mean infested) with rats. They were in the walls, roof, outbuilding, under the floors and in the kitchen. (the house is old and wasn’t lived in for a long time)
I saw them climbing up to a swallows nest and eating the eggs so I know that too many rats can do damage to wildlife as well.
This study that was linked to from Miguels post is fascinating. Talks about removing cats can create an even worse problem for local wildlife. Well worth a read.
The cats in my case controlled the rat population within a few months. Still plenty of rats but not a plague. They also preyed on insects such as grasshopper, very few but about 6 birds (that I know about) and a lot of voles. Also preyed on lizards and sometimes a snake. They definately had an impact but there are still good populations of all the above creatures mentioned and also many more birds nests than before. (beacuse of less rats)
We have moved to a village house now and the cats are indoor cats so they could be classed as retired.