> Is land tax really more propaganda resistent?
Yes. Capital interests have spent the last 50 years laying minefields around the concepts of socialism. "Socialism is when more taxes," "socialism is when unions stop your employer from paying you more than your lazy coworker," "socialism is when you own nothing (as in property, not just assets)." Focusing on small, concrete reforms allow you to navigate around the mines.
> Isn't class conflict a direct and inevitable result of private ownership of capital?
No, it depends on the terms of ownership. Finite terms and progressive taxation can prevent the exponential runaway that establishes and perpetuates class structures.
> What kind of arrangement makes companies pay more for labor than they have to?
Policy that makes labor less desperate and therefore have higher bargaining power. There are many levers to pull.