Should I punish a kid for drawing swastikas on his paper?

So for context I am a 17 year old female in my junior year of high school. I am currently enrolled in a teaching program through my local technical school that allows me to observe in a classroom for the first half of my school day once a week. I am observing in an advanced 7th grade English classroom because that will likely be my field. I have been doing this since about a month and a half into the school year. I have tried to always have something to do with the kids when I come as the teacher I’m under is one of my old favorites and gave me explicit permission to run activities with them and essentially do whatever. Today the students finished up a creative writing activity we ran out of time for last week. Upon completion I collected their papers and went down to the other class that I finish my time in (still at the school where I observe). There, I started reading through the stories they had created and discovered a paper with several “doodles” at the top that could be excused as random scribbles… but they got notably more swastika-like until the last one which is a swastika no doubt about it. They were almost all lightly scribbled over (still entirely visible). I was disheartened to see this and went up to speak with the teacher of the first class but he was on break so I left a note and then emailed him later to explain. I’ll leave what I said in quotes: “ I was looking over the papers from the challenge activity I ran with the kids in teachers name’s room and found a series of concerning drawings on one student's paper. I will attach a photo below. I am hoping to speak with the student personally next week, to address this. My goal is ask kid’s name if he knows what the symbol is called, and its significance etc before any punishment is given because I want to believe that he is ignorant on its history. Please let me know your thoughts on the matter. With regards, My name” He replied back quickly and let me know we’d definitely speak with him and that he found the behavior unacceptable. I thought, as my part, if I find he did it maliciously I will have him do an alternative assignment next time I run a fun activity, something along the lines of “write a paragraph detailing the harm hate symbols can cause”… at home I brought this up to my dad who had a surprising reaction, seeing as two teachers and several friends I spoke to all agreed this was the best course of action. He looked entirely indifferent and when I said that I planned on talking with him to understand his motivations and explained how he’d be given an alternative activity/assignment by me next time I was there and that ultimately the teacher would punish him as he sees fit be it iss (in school suspension) or lunch detention or what have you he told me that it would be quite unfair to give him iss for that and that he couldnt, even shouldnt, be punished for just a drawing, and that it wasn’t directed to someone etc. I personally think this is entirely unacceptable behavior and told him so and he looked at me like I was crazy. Then he told me I could read up on how many countries have used that symbol before the Germans made it bad and that everyone who sees it thinks one thing but it’s meant a lot before. Don’t get me wrong, I know it wasn’t always a hate symbol but quite frankly that’s what it means now and I was rubbed the wrong way by his response. So, I wanted to ask the community if they think I’m being unreasonable, as that’s not my intention, hence the (sorry- really long) post. If you made it this far, thank you and please let me know!