People at NRA conventions can carry guns. It's on their website.
https://www.nraam.org/attend/firearms-policy/
"During the 2019 NRA Annual Meetings & Exhibits, lawfully carried firearms will be permitted in the Indiana Convention Center and the Lucas Oil Stadium,l in accordance with Indiana law."
The White House is a federal building. There are laws against carrying firearms in federal buildings unless you're part of the agency protecting the building.
Your argument is a fruit salad. First it's the white house, then you're comparing a federal building to a private organization (and getting it wrong)...