Naked pictures on husbands phone

So my husband and I don't hid anything from each other and we don't go through each other's phones but last night as we were sitting together he kept getting messages from his friend I opened then and they were all pictures of naked women. I instantly got upset and he doesn't understand why. He friend is and old nasty man and to me it's disrespectful to me for him to be sending stuff like this to my husband and my husband doesn't understand where I'm coming from. Yes guys will be guys and you can't keep anyone in blinders their whole life but having other naked girls all in your phone and not deleting them because he doesn't want to delete the whole conversation...? It just it's flying with me. Am I overreacting? Mind you I'm 26 weeks pregnant, emotions all over the place and this just makes me feel insecure.

***update***

So I just want to clarify...I'm not upset at my husband because his friend sent him nudes pictures of women I feel disrespected by his friend because he certainly knows he's married and has a child with another on the way and if he wants single friends he can share that stuff with he needs to go find them elsewhere. I am in fact upset with my husband because he didn't say anything to his friend about it. Sure he wasn't hiding it from me by any means but it's still pictures of other women on his phone that aren't me...and it's like he doesn't understand or take in consideration how it will make me feel seeing that. Like how hard is it to just say "hey man that's inappropriate my wife wouldn't appreciate see that shit don't send anything like that." No to him it's no big deal because he just brushes it off and he's not pondering over them. It also really makes mad that I have to tell him this and he doesn't realize it on his own😡

**update***

So I'm still furious because my husband still doesn't understand what is wrong and why I'm upset because he "didn't cheat on me" but to me it's disrespectful and kinda makes me feel like I'm not good enough because he obviously didn't delete them so he's keeping them there so he can look at them. Plus he doesn't have the sense to say something to his friend and stand by our relationship in the first place. And if there were dick picks all over my phone he wouldn't care as long as guys weren't sending them. But what do I need other guys dicks on my phone for when I'm married and have one to go home to every night. I am so fed up at this point why are guys so stupid.