HWD
You are the first to mention a resolution advisory! Do you know what happened in the case in question? If it is the case I am thinking of I seem to remember it was a TA, not an RA, although that is one detail I cannot recall with certainty.
Where did anyone assume a class D bust is not dangerous? I said they are not usually dangerous - rather than lambasting perhaps read more carefully! I have seen and heard a few, even to my shame had one, none of which were anything more than an annoyance and extra work load for ATC (or just a sharp reminder over the radio in my case). At Gatwick they are likely to be even less dangerous, due to the closer ATC monitoring, although far more of a nuissance.
Agree that any airspace infringement is something to be taken seriously, but there are degrees, and there are different responses that can change the seriousness.