I'm of the opinion that dishonesty is serious because it's an irreconcilable breach of trust. There are many things I'm happy to deal with internally providing there's a frank account but once someone intentionally misleads another it makes individual management untenable.

Separately it's a HR problem because of the nature of certain types of work. I'm struggling to fit my view with neural diversity though - some devs say dishonest things without malicious intent because they lack skills to effectively communicate.