By this time, the identity of the young professor had already been exposed at the U.S. National Security Agency. Although they hadn't made it public and even seemed to be completely oblivious, Ren He harbored no illusions about their ignorance; the group was probably silent because their own activities weren't exactly clean either.
Kidnapping the Chinese ambassador, even in secret, is not a good look diplomatically for anyone involved. Even though Yang En had changed his appearance and assumed a different identity, the problem was he was still an ambassador after all.
If they caught you, they could pretend to not know, but if they didn't, well, better just give it a rest.
In fact, this is the nature of espionage—no one wants these actions to escalate to the level of politics.
