The interview with the hiring manager/s was positive. I was genuinely looking forward to working for them.
The individual in HR who gave me the verbal offer was the issue; they tried to assassinate my character with no discussion permitted because I was disappointed with the compensation package vs. the amount of work that was going to be expected of me. They claim their offer was "equitable," but validated data provided by Glassdoor for a similar position at that level shows they were $25K off the mark. They claimed I was unruly because I sought to negotiate and present my case to the hiring manager.
Essentially, AIG had an employee who did not understand the position or the work involved attempt to discredit me simply because I welcomed a counteroffer to their initial lowball offer. Incredibly unprofessional.