Unfortunately lying is a necessary part of life. No one can be 100% honest as then they would have no friends and/or partners because no one wants the truth 100% of the time. As for lying to prevent an argument I don't see why that is a problem. People do it all the time and it can be a good thing. If you know your partners triggers and choose not to make them angry over trivial things then that seems like being a good partner to me.

Obviously what you choose to lie about is key. There are bad lies and good lies so it really is a slippery slope when saying that lying can be acceptable. Personally I think that if the situation stops at the lie (ie arguing with parents and she asks your opinion. Yes honey I agree with you) it is acceptable but lies that can come back and have damaging consequences should always be avoided.

Anyone who thinks that lying is completely unacceptable should try and go through a full normal day (work, kids, spouse, friends, family etc.) and be 100% honest with everybody about everything and see how things turn out lol.