I believe this was Charlie's first role or his first major role. Even if he had certain viewpoints, I think the excitement of being in the movie would have outweighed them. And since he later plays some roles his dad probably wouldn't like, I don't think politics was too much of a problem for this movie for him.

Haha, exactly. Any actor who turns down parts especially due to political leanings is probably some overrated hack, anyway.
Acting like you some one-man GPS

I think it'd be a shame if actors let their beliefs get in the way of a good role.
Definitely. I mean, they call it acting for a reason. Pretty sure Bella Lugosi didn't go around biting people on the neck in real life, but he didn't let it stop him from playing a vampire
.

A journey into the realm of the obscure:
http://saturdayshowcase.blogspot.com/

I was watching the red dawn documentary and it said some of the actors in this were liberals (Jennifer Grey especially). I think it'd be a shame if actors let their beliefs get in the way of a good role.
Acting like you some one-man GPS

Ahhh, I'd forgotten about the elder Sheen and
Apocalypse
. That's likely the connective thread right there.

A journey into the realm of the obscure:
http://saturdayshowcase.blogspot.com/

I reckon Milius cast him because he wrote Apocalypse Now and Charlie Sheen was there on set quite a lot when they were making it, so he just kind of knew him from that and because of his dad, and was told he was acting, and just chose him?
Despite his dad being a die hard liberal, I don't think Charles holds the same ideals and I'm sure Martin is cool enough to let his kids choose their own path. Charlie went on to play a Navy Seal and a few other flag waving roles. I doubt his dad approved! Charlie's banker wasn't complaining.
Acting like you some one-man GPS