Is "poo" a swear word?

I'm surprised anyone finds it to be a swear word. My stepdad (47m) questioned me (21m) for using it. I said, "There was some poo" in regards to the toilet. He said, "Poo?"

Here's the context:

My brother's dad [47m] is raising a ******* tattletale and he [9m] doesn't know it. He's responsible for all the crap that I have questioned yet he takes offense to my anger. I wasn't having a "trigger" or a "blowout" as my mom [45f] accuses me of having, but I was implying that even a kid with half a brain would check to make sure to flush the toilet completely.

The toilet had some piss and poop, I asked who forgot to flush it. I knocked on the door but the parents weren't available for discussion at that brief moment. I said to my brother, "You know what- I'm just gonna pretend I didn't flush it" just to put the blame on myself since "no one wants to take responsibility."

I flushed the toilet, only peed and reflushed, and my brother was accused of sharing "too much information" that he (and I, too) are informed not to discuss poop or pee with anyone BESIDES the parents.

A lot of kids' shows/movies make pee and poo jokes. Doctors/nurses discuss pee (urinal) with patients. What's the ******* big deal?