Try turning the statements into genuine questions. For example: "I don't know but, the library you are using is bloated compared to library X". That could be tu

Try turning the statements into genuine questions. For example: "I don't know but, the library you are using is bloated compared to library X". That could be turned into "Isn't library X much smaller than the library you're using? Do you need that big of a library?" Or even "I thought the library you're using is considered bloated compared to library X." It's a gentle way to get the other person to explain themselves.