Always take her side

Recently got into an argument with my fiance and without exposing too much information he basically blamed me for everything and took a side (not mine obviously). It finally hit me why men who are married always say take her side wether she's right or wrong and not just because the steryo typical "because you'll really be in for it later" which yes you maybe (if you don't), and this is why, In a moment or situation where everyone is against you, the last thing you need is for your best friend, who you trust is to turn against you and not be there for you. Simple. This is visa versa of course it doesn't just apply to the men. Tell me what you guys think, agree? disagree?