Why is it okay for missionaries to lie?

[HoreTore]

You are making an assumption of dishonesty, and how can dishonesty not be negative?

Whether it's positive, negative or neutral to lie(or "be dishonest" if you prefer) is based on the context. In this context, I'd say it's neutral and more of an interesting feature than good or bad.

You default to the negative judgement about religions and religious people, always.

I see no reason to respond to this statement.