If you read the LKML thread with Linus' rant, you would know that big endian ARM* is a problematic part of the Linux kernel that the maintainers are removing due to lack of testing let alone receiving bug fixes. It's also implied that big endian causes problems elsewhere beyond ARM, but no examples are given.

Later on in the thread, Linus states that he has no problem with historically Big Endian architectures, it's just that nothing new should be added for absolutely no reason.

*ARMv3+ is bi endian, but only for data, all instructions are little endian.