DW, I think I know what Pyr is saying. He's saying that applying mental force to get someone to do what you want is morally questionable or even outright bad. Instead you should consult them about what they want and work with that. I recognize this as a kind of idealistic goal in human interaction, so let's work with that for a moment as assume it's a coherent goal.
What sorts of interactions in human society make use of persuasion where you finally get the person to do something other than what he/she originally wanted to, but where the final result is 'agreed' upon? If persuasion is going to be considered off-limits let's try and figure out which parts of life will be considered off-limits.
-Obviously advertising will be illegal, as its entire basis is in persuading people to do things. Sometimes it's borderline brainwashing, so advertising is right out. Likewise with attempts to market to customers or compete in any overt way.
-In business neither party in a transaction tends to accept an initial offer, and a negotiation must be made with each side trying to get the most out of the other. This will obviously be off-limits, and price negotiation will be illegal since it's 'coercive.' Market-based economics cannot function without initial disagreement and either one side persuading the other or a half-way point decided upon.
-There can be no moral education, since education (especially in young people) requires convincing someone that what they are currently doing, or at least naturally inclined to do, is harmful and should be stopped. Ironically this includes trying to persuade people that persuasion is illegitimate (!).
-The legal system is currently based upon two parties (lawyers) persuading a third party (judge or jury) of the merit of a case. There could be a legal system without persuasion, but the current one is based upon persuasion and so would obviously have to be scrapped.
-Jurisprudence and Congressional work also involve a great deal of persuasion. Even setting aside corruption for the moment, the activity of politics appears to mostly reside in the attempt to convince others to support or oppose a cause or a bill. Since this would now be considered as an assault jurisprudence and law-making as we know it would be scrapped in favor of another system.
-Friends who want to go out to the movies might have to all split up and go see different film alone, since persuading your friend to see the movie you want to see would be assault.
I think I can stop there. It should be evident by now that what I mean to say is that most human interaction of any kind involves persuasion and - ideally - agreement after the attempt to persuade or negotiate are concluded. Without each person being able to push their own idea of what should happen next, which in turn results in some kind of agreement being hammered out, then you have not only the end of personal agency within society, but also the end of society as we know it. From an idealistic standpoint maybe there would be something good about this, and indeed I wouldn't entirely be against the abolition of some of the cornerstones of culture as we know it. But typically when someone throws out a broad sweeping idealistic statement it will rarely come along with what the real consequences of its implementation would be. The words and the reality remain separate from each other, which is probably why the word "idealism" is met with such derision in most circles.
As DW has pointed out, it is Pyr's formulation of "persuasion cannot lead to consent" that is the issue here.