this past weekend, I attended my best friend's wedding. I ended up sat next to the groom's younger brother (this will be important). The ceremony went off without a hitch, no objections to the union, no awkward vows, etc. However, after the officiant pronounced them "Man & Wife" and we were all applauding, the younger brother shouted "Let's Fucking Go!!!" I reacted by sort of scoff chuckling, "Ho ho hoh my god." The bride noticed both of these things happen in quick succession. At the reception, she accused me of putting him up to it, because she remembers how the groom and I used to pull dumb pranks and act like "Frat Bros" in college. I told her the truth, that I didn't put him up to it, and that I was just caught off guard by the outburst, and that is why I laughed, but she wasn't convinced. She is now telling her husband that I am not welcome at their home until I apologize publicly. For the record, the brother is getting off scot-free because "He's young and didn't know better." So, Reddit, am I the asshole?