Alternatives to supervisor for letter of recommendation
I am no expert on MBA admissions, but I believe they are looking for letters attest to qualities beyond the ability to do well in school, such as entrepreneurship, community service, leadership, and so forth. If your current boss--it sounds like that's what you mean by "supervisor"--is as weirdly hostile as you say, don't ask him for a letter. Look for other respected people in your network who can speak to the qualities MBA programs are looking for, such as administrators, elected officials, community leaders, or even clients.