I'm just wondering why you should be so incensed about the fact that cats catch the odd bird?
I'm not incensed in the slightest, just bemused that some people seem to lead very blinkered lives about just what cats do, and therefore where lines of acceptable behaviour for cats can be drawn if looked at pragmatically.
Cat kills bird = it's just its instincts, no need to worry, plenty of birds
Python kills cat = it's just its instincts, no need to worry, plenty of cats
Those two scenarios are almost identical, but for the fact that the second encounter has less effect on the natural wildlife of this country than the first. Neither cats nor pythons are native, wild creatures in this country, but the birds moggy tortures and kills for fun are. At least the python was probably hungry…
As for your bluetit analogy – I'm not daft or irresponsible enough to raise a cat. I guess the bluetit's mother feels differently about her chick…