As long as the person is not being a plain aSShole, I will try to make them understand and ease the misconceptions but I don't have the time to deal with people who wouldn't even try to understand it. It's not worth my time.
I don't see the need to defend an anime or anime in general. Everyone is entitles to have their own opinions and it's useless to try and argue with people about how good something can be.
I won't defend anime at all. If people were to talk trash about it, I would ignore them and it's not like I have an obligation to defend it. Most of the time people do it to rile up others.