OXON HILL, Md. — A year ago, attendees at the Conservative Political Action Conference, the annual jamboree of the political right, were greeted by Big Tech with open arms and open bars.

Google sponsored a lavish hospitality suite, courting conservatives with an outdoor fireplace, hors d’oeuvres and flowing cocktails. Bright young representatives from Facebook hosted a “help desk,” handing out cookies frosted with emoji icons and offering free demonstrations of its virtual reality product, Oculus.

That was then. At last week’s gathering here in a suburb of Washington, Silicon Valley’s only obvious presence was on the lips of exercised right-wing critics who whipped up the crowd by denouncing the American tech industry as an authoritarian hegemony intent on censoring their cause.

“Facebook, Google and Twitter are pushing a left-wing social agenda while marshaling their marketing power to shut conservative voices out of the marketplace,” said Senator Josh Hawley, a Missouri Republican, during a featured session with the ominous title “Blocked: This Panel Has Been Removed for Conservative Content.”