Mark Rowlands attempts to distinguish legitimate and illegitimate means of belief-changing by appealing to "Wilfred Sellars’ distinction between the space of causes and the space of reasons." Geoff Arnold is not so sure this (supposedly) objective distinction really captures the ethical distinction, invoking blatantly false arguments as an illegitimate means of belief-changing which intuitively falls into the same objective "space of reasons" that a sound argument would fall.
But I think there's a deeper critique: There's no objective difference between the space of reasons and the space of causes.
All reasons, all arguments, indeed all speech (and writing) is inherently causal. When I speak to you, when you read any words, there is a well-understood physical causal chain of events which makes actual physical changes to your brain. Reasons, at least those actually communicated from one person to another, specious reasons as much as sound reasons, all create irreversible changes in the listener's brain. Reasons are causes; the objective distinction between reasons and causes is illusory.
I think Rowlands is just over-thinking the whole thing. (Quelle suprise, a professional philosopher over-thinking an ethical question.) There are certain methods (e.g. speech, argument, verbal exhortation) that we in the West typically approve of to attempt to change another's mind, and those methods we do not approve of (e.g. lobotomy, brainwashing, blows to the head); these methods have become social, cultural and legal norms. (Even more severely they are specifically Western norms; I don't think Ibraham Lawson (or neoconservatives) would find Rowlands intuitive ethical evaluation as compelling as Geoff Arnold or I do.)
The rationalization for these norms is simply pragmatic: It's better to employ relatively painless methods to change people's minds. The cause of these norms being actually prevalent in Western society is historical, contingent and evolutionary.