Does this frustate anyone else

I just read a thread about spanking your child. I have a 2 year old who is pushing the boundaries so much that she will not listen to me, she won't go to sleep or nap during the day :( I'm completely buggerd, I have a 7 month old as well and im so frustrated with my daughter that when I have tried everything else my last resort is a smack on the bum or hand ( not hard to leave a Mark but firm for her to know I'm serious about what she is doing needs to stop) it still doesn't work but anyway this ladie is pregnant and was full saying how she is against it and she has other methods to try and it won't need to get to that.. She is a ftm I just think ftms judge others when they haven't been there yet, I always thought I wouldn't have to get to the point of smacking but I have, I just think it's wrong for them to judge others when they haven't dealt with that before.. am I wrong to feel this way