Completely? Yeah, I don't see it. Maybe because I'm German and there's very little fuss made about nudity over here*, which in turn makes me very confident it's just a cultural thing. Society taught you that there's something special about genitals, so you start believing it. Most people can probably overcome this through simple exposure or doctors would have a problem.
What's going to matter more is the setting. I'm guessing the pictures are supposed to be sexual, which might affect viewers more than the fact it's a picture of a penis.
> There are many women who are traumatized by getting sent dick photos.
I'm sorry, but if seeing a penis can traumatize someone, there's something wrong with them - and it's not the fact they've been sent a dick pic. It doesn't excuse others being intrusive or exploiting that vulnerability, but it's still a vulnerability that is way abnormal and should probably be addressed.
Overall I agree with you that it can affect someone, but I'd do so with more nuance than using words like "trauma".
*There's way more "extreme" examples than Germans, even ignoring our animal relatives.
I think the Anglosphere's over-sexulisation of any and all nudity makes it worse than it needs to be (I think my exposure to e.g. Germany's sauna culture on a few trips has really helped me form a healither attitudes to nudity in a dozen or two hours than the rest of my life over here, and that kind of thing being more common would probably help people be able to more easily shake it off) but I think the tramatic part is the stalker behaviour and being directly targeted by someone with a lewd motive. And it being done when the person sending it knows it's undesired and forcing them to look is kind of almost rapey.
So for me, I'd find it creepy if somebody was targeting me with that, but would have zero issues approaching it from "I'm here to filter out the dick picks so I'm going to see a lot of anatomy". This is very different to e.g. gore where I actualy do feel a bit physically sick if I know it's real, but if I randomly see nudity that's not motivated at me it's basically nothing.
USA and UK are just exceptionally prudish (by Western standards at least).