What is the exact problem here? Who would be doing a MITM attack on someone and how?
It doesn't seem to matter to me if my ISP is MITM, because someone inside the ISP would need to cause that. If my ISP is forced to MITM by government etc, I am in trouble anyway.
I could see that it could be done by using a bad/spoofed wireless or a public network connection somewhere. That makes sense. I don't do that though; I only use my own secure home network in a wired fashion when accessing my bank account.
If people are able to spoof my network connection, they could interfere with non-https software updates on my machine, which would let them replace the root certs of my browser potentially, in which case https wouldn't matter. Is the assumption here that all software updates on my machine are happening via https and only the bank website is a danger?
My point here is that while I agree what the bank is doing is bad practice, I don't see how it would affect me in any way.