Just like people say that ...DIL is like a daughter to me..
my MIL is like a mother..
My daughters are like son to me..
But I would say that..
Why not love you dil as a DIL only..because daughter is totally different, nobody can be like her, but one can love another person also in her own role if she is good to you.
Same MIL can never be your mother, Mothers take every thing from their daughters even trash and you can take them for granted,but with MIL one has to have certain courtesy, and show some respect and restrain, otherwise your relationship is doomed.
And last one, though people say it to show their love to their daughters, I feel there cant be anything more insulting than this...why not love your children just like that?