People in general don’t work by any guiding principles, they work by emotions. Emotions don’t care about consistency.

Acting in a consistent way has to be learned in a rational way, and it involves suppressing your emotional reaction. People are only lile this if they explicitly learn/practice this, the default human without learning that does not work like that.

So, the fact that your dad is good to you and bad to other people is very simply explained: he loves you, acting lovingly, and hates others, acting hatefully.