Lies to the ingroup are bad. Lies to your enemies are practically mandatory.
Problem: your enemies will doubt you, because they're your enemies. When Red America lies to Blue America, the DNC doesn't have a crisis of confidence, they just laugh at the lies. "You thought that was believable? lol"
Conclusion: if you lie and it works, 98.4% of the time it was a lie to one of your friends, thus a betrayal, thus literally the peak of evil.
Corollary: "Lies are bad, mmmkay."