Two year old boy vs. Ten year old cat

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I have a two year old boy that has just recently decided he wants to show agression towards the cat. We thought at first it was because he was frustrated because he got into trouble, so he would go and pick on the cat (try to kick her, hit her, and pull her fur). But yesterday, he had not been in trouble all day, and was sitting on the bed with the cat and I was peeking around the corner to observe him, and sure enough, he pulled a clump of hair out of the cat! My response to this is I tell my son, "NO! We do not hurt the cat" followed with a spanking and I put him in time out. After his time out, I get the cat, I take her to him and ask him to apologize to the cat (he's only two so his "apologizing" is usually a hug or kiss) and then I show him how we pet the cat and show her love. What is surprising is how tolerant the cat is of him. She has always been some what of a non social cat and usually runs but she is very tolerant of him and just sits there and takes it from him. I almost wish she would give him a bite or a scratch so he knows not to do it and that she doesn't like it. This has been going on for a couple of months now and I am not sure if this is normal for kids (seeing as this is my first) or if I am doing wrong or missing something???? Anyone with some experience on this?