Doubt it. Have RN ever got majority in France to make this assumption?
Also "brainwashing" as you call it is allowed. Unless you mean they actually got people in a room and turned them into left-voting zombies by injecting something into their brain. Again, doubt that is the case.
RN would never even get majority due to all the other parties, even those who aren't aligned, clumping together as the muh anti nazi allaince and vote harvesting accordingly. But as i said, even if they did get into government, they would do NOTHING. Nothing ever happens. System prevails.
Yes, brainwashing is allowed. In our society, those, who have more money and are connected together for some goal, no matter how evil, will be able to condition dumb masses to do what they want. Can say it's legal, of course, but it's immoral and anti democratic. It's oligarchy, to term it mildly.
Only cases of sort of democracy that have ever existed, were within smallish homogenous communes, where people know each other and there are no subversive foreign or shadowy elements that can sway the pendulum. And even then it wasn't really universal, but based on caste, social status.
tl;dr - there is no such thing as democracy in the West. It's a sham to direct people into their places, without excess violence (although some is still used).