But social skills are not spells or attacks. They do not have the force of such things and don't take away the players agency but help direct that agency. It's called role playing. Your character might be talked into things he wouldn't normally do but yeah that's what happens when dealing with incredibly characteristic people! Why wouldn't you just role play that.
You're right, it
is roleplaying but it is just one flavor of roleplaying. But it's, effectively, the director telling the actor "act this way..." Instead of the actor deciding how they think the character should act. Sure, sometimes the players make choices that I wouldn't choose, but that's why D&D is different from, say, a play.
I believe the social skills are there to allow the DM to be neutral when taking on the parts of all those NPCs. As a DM I don't want to have to decide if my NPCs are persuaded or deceived or intimidated by the PCs. I'd rather roll the dice instead of having to decide if my NPC would find this particular argument compelling. Because that would be the player persuading me, not the character persuading the NPC.
Do you imagine a player is going to have fun if you force him to act in a certain way, to comply with your notions of roleplaying?
Here's something to consider: don't take a high Persuade roll to mean "you persuaded the target". It just means, "You made a persuasive argument." How others react to that persuasive argument is up to them. It might be, "Yeah, Mr. Bard, I can't really find a flaw with your logic, but you always do that with your fancy college words. I'm going to dig my heels in even more just to spite you." Or literally countless other reasons why the person wasn't persuaded. (You might want to encourage your barbarian to play around with this sort of thing. Don't tell him to do something different, just ask him to...you know...
roleplay his choices.)
I'm
sure you've been in the situation where somebody has presented an argument in which you can't find any holes, but it still doesn't make you change your mind. Right?
Just let everybody roleplay in the way that they enjoy. If you really can't handle that, don't invite the person who has different opinions.