Let me make a wider comment about backwards compatibility.
The community has already messed up backward compatibility in far more obvious and wide-reaching ways, for far worse reasons, many times. Suddenly deciding to stand on principle, in a case where the current behavior is *clearly* wrong and dangerous, seems "off" to me.
Of course, you're welcome to do it... I'll just have to make sure it's understood that the decision was made to enshrine actively dangerous behavior.
(I could make an argument for this being CVE-worthy. In fact, Austin Seipp has already made most of it. Should a major security hole also be protected and propagated by a sudden need to stand on backward compatibility principles that have never been given much more than lip service in the past?)