Attending events as a plus-one can be a stressful undertaking for anyone, especially if they're work-related. As a guest of a guest, you want to make a good impression and shine on your partner with a complimenting light. But in some cases, the partner makes that intention practically impossible.
The original poster's night at her boyfriend's work Christmas party was exactly like that and was quite the spectacle. Her boyfriend, apparently fancying himself a comedian, decided to use OP as the evening's entertainment. He mocked her career and shared embarrassing personal stories she'd asked him to keep private because nothing says "I respect you" like public humiliation.
Our event planner showed remarkable restraint as she endured a series of "jokes" about her profession. Being told she just "plans parties" while surrounded by "real" professionals must have been a real ego boost. The boyfriend's routine peaked when he shared that personal story she'd specifically asked him not to tell. Clearly, her wishes were less important than getting a few laughs.
OP eventually decided she'd had enough and left. BF aka Prince Charming, who understood where he went wrong and wanted to make amends - came home only to double down by accusing her of embarrassing him. Because somehow, she was the one making him look bad, not his stellar performance of depreciation.