Joe Macarty had to find different sources and different crimes to charge spies with that were proveable yet didnt require revealing we were listening directly to communications between moscow and its spies in the US. Joe Macarthy coulnt just Kill them he had to find other crimes he could prove then charge them with that crime. The venona papers declassified this information and showed macarty as doing the right thing. This was on US soil however. That said you could argue the spies were a greater threat yet we still didnt just shoot them