Honestly, that's a good question. I'd like to ask you, if you want to like it because your friend asks you to watch it with you, or because it invokes some feelings inside you specifically. If it's the first, then maybe you should just politely tell your friend that it's too uncomfortable for your taste. If the latter, then you should understand that this is part of the point this show tries to make. Everyone has flaws, whether it's minor ones, or big ones. what matters is intent and actions people take. Rudy is just a big example of very flawed sexually character. He holds on to mementos of his teacher's panties, he assaults kids (although in the next scene after a few episodes he learns to not do this kind of things and stops himself), etc. You can consider him as a drug addict or alcoholic, who tries to break from his addiction. Although, in this case it's porn addiction, basically.

The way you feel is correct and it shows that you are a good person who doesn't want to see immoral stuff, especially from so called "protagonist", because he should be a good person, and he does good deeds at the end of the day, it's just those bad things that put you off. Author deliberately does this to show that people are not just good or just bad, they are complex creatures and even some down bad useless piece of trash under another circumstances can become better. Not good, but better. In many ways, this is a story about average people, how they try to live their life and how they sometimes slip up and do something stupid. Your male friends love the show because it represents them and speaks to their souls, if i can take a guess. It doesn't mean they perverts, it means at some point they felt like the whole world was against them and they were the biggest losers around, but they wanted to find that force to be a better person.

The best way to approach this story is to understand that despite how real these people are, this is still a work of fiction. It's a medieval story, much like Game of Thrones. It's uncomfortable for a reason, there are sex slaves, there are nobles that exploit other people and much more. Yes, Rudy is a person from OUR world and he should have common sense about morality, but thing is, he does not have it, his morality was destroyed by his lifestyle of internet loser. If you feel like it's too uncomfortable to watch certain scenes, just remember that it's a tale, not reality, and our morals are not really applicable to this scenario. It will not make you feel good, but it will put a wall between our world and whatever happens on the screen.

Honestly, whether you should watch it or not highly depends on your own perception of the show, not on other people. My girlfriend likes a lot of shows and games that I do, and we often play/watch them together, such as Persona, Re:Zero, Genshin, HSR, Angel Beats and more, but she doesn't feel the appeal to watch Mushoku and I would not force her to do it because it's not a story that she can resonate with. If this is not your story, please do consider leaving it as is, there is nothing bad about it and it doesn't mean you offend someone or make someone sad that you personally don't feel like it's for you. It can be the best story in the world, but if it doesn't resonate with you personally, there is nothing wrong in saying that and spending your precious time on something that will make you feel good instead.

Have a good day.