Nobody wants to lie. We only do it because we are afraid of what someone might say or do in response to our truth. People learn to tell you the truth to the extent that you unconditionally accept what they are saying and who they are.
To lie is always an error for many reasons. But putting someone in a position where they feel the need to do so is much worse. Nobody has the right to project their own arbitrary preferences and tastes upon someone else through a set of rules and expectations, and then attack or call them a liar when they cannot comply. This shows zero love or respect.
When you understand this, you can easily forgive lies is by making it 100% clear that, with you, there is no need to hide anything. You can always accept someone's truth calmly. This creates the space, the trust, the openness required for a beautiful relationship to flourish.