It was a political statement.
Peter Stanley explains his prank, committed during the height of the AIDS epidemic:
On September 5th, 1991, I put a giant condom over Jesse Helms’ house.That's why Mr. Stanley and his fellow activists decided to have a good laugh and make a political point at Mr. Helm's expense.
Why? Because, as the condom said, “Helms is deadlier than a virus.” Senator Jesse Helms was one of the chief architects of AIDS-related stigma in the U.S. He fought against any federal spending on HIV research, treatment or prevention. He once said, referring to homosexuals, “it's their deliberate, disgusting, revolting conduct that is responsible for the disease.” Here’s another choice one: “There is not one single case of AIDS in this country that cannot be traced in origin to sodomy.”
By saying words like this on the floor of the Senate, Helms gave a veil of legitimacy to every parent who threw their HIV positive kid out of the house. ACT UP New York was filled with angry young men who experienced this kind of Helms-related hatred.
Read more: The Condom on Jesse Helms' House, Actipedia>>