Why is rude allowed?

Why are we supposed to let our children hurt our feelings?  I understand that children are not born with sensitivity chips and don't automatically know when they say something hurtful.  But is that really an excuse.  We do what we're supposed to when our children point at some one who looks different or ask too loudly about some one in a wheel chair, etc, but we tend to let our children say mean things to us, the parents, because "they don't know better".  

Many of the things our children say to us, we would never tolerate from an adult.  I understand that our children get frustrated and angry with us, but we need to teach them how to properly express that anger.  If a friend of mine told me I was stupid the way my daughter does, I would tell them that hurt my feelings and we may not be friends anymore.  When my daughter does that to me, I'm supposed to be the "grown up" and get over it without an apology because she's "just a kid".  I think my daughter is old enough now that when she says or does something hurtful, I stop talking to her for a while.  Now, I don't pout like a toddler or run off and cry.  I just inform her that she hurt my feelings and I don't wish to talk to her anymore.  I won't help her with a puzzle or get out her crafts because she was mean and I should not be obligated to do nice things for her if she's not nice to me.

The other adult in my house thinks I should put her in time out or make her do sit-ups for punishment.  (Sit-ups have worked fantastic for us as a quick punishment for a sassy mouth.)  I think it's more important to give her a real world consequence.  If she's mean to friends or strangers they aren't going to put her in time out, they aren't going to play with her or help her.

It's not like I stop talking to her for days, just a few hours or until she honestly apologizes.  I think we send a confusing message to our children when we tell them to be nice and share with their friends, but we don't expect them to behave the same toward us.  I also think it's important for my children to know that I'm a person and I have feelings just like anyone else.  Now that I stay home, I really get abused.  Kids say really mean things and I'm their target all day long.