Words like retard need to evoke offensive imagery in order to fulfil their intended purpose. If they didn't, they would be interchangeable with regular speech. Calling someone "pimple t thumblehopper" simply doesn't evoke any sensationalist reaction; it evokes laughter in the face of the speaker because it sounds so fucking stupid.
Which part of that paragraph caught your attention? Was it the last part? Be honest.
"But can't we agree to at least use benign insults?" You can't, there's no such thing as a benign insult. Name one. S-t? It evokes negative body image: harr! you're unclean because your body expels waste products. A----le? Same. B---h? Sexist. C--t, p---y, m---e! Harr, ladyparts betray your effeminate qualities, and being anything like a w---n is baaad. C--k? P-----s, and men, are bad too. It's male-shaming, by god. C--------r? C--------r? M----------r? F----r? Sex is dirty, submission is vile! Where, how, and by what measure, does one draw the line between these perceived harms and the perceived harms perpetrated against the gays, the blacks, the gypsies and Jews?
We adults may use our brains to determine when provocative language is appropriate and when it is not. I wouldn't call someone a "fucking retard" if they actually had developmental issues simply because I don't know how they would process that and I do try to make a token attempt at sympathy; they're the sole exception, and I'm still going to say it to my heart's content when I'm sure they're not within earshot because I know full well that I'm capable of regulating my own prejudices within the context of real-world behavior, the only time my opinion of any particular group actually matters. To their faces, I am polite. I am patient. I recognize their subjective value as members of the common species. I acknowledge their basic right to exist. My casual use of a word that they cannot hear, and that doesn't necessarily dampen my appreciation of their lot in life, is effectively meaningless.
I submit that not everyone who uses insensitive, chauvinistic language is inherently and absolutely harmful to its respective inspiration, however marginalized that inspiration may be. I say that as someone who was marginalized at the most vulnerable stages of life, as someone who has first-hand knowledge of what it's like to be on the receiving end of offensive language, insults and the phenomena for which they stand. I say that, again, as someone who can differentiate between absurdities and actual perceptions of whole peoples.
I'm... the product of childhood physical, emotional and verbal abuse. I've struggled with depression and suicide for nearly my entire life. I've also had facial paralysis for the last ten years, and an admittedly small, remote portion of my ethnic heritage is derived from a group of people who've been persecuted since antiquity. These conditions have significantly affected both my life and the way I interact with my fellow human beings.
Despite this lifetime of experience, I can't help but respond with scepticism when "victims" or, perhaps more tellingly, the "family and friends" of the victims claim righteous indignation and apparently wilt like lilies at the mere mention of words reminiscent of the traumas they have endured. In my own experience, overhearing insensitivities, or even having them said directly to my face, pales in comparison to the experiences themselves to the extent that I laugh defiantly in the general direction of the people who would defend my alleged delicate sensibilities. If anything, I'd be more inclined to feel insulted by the white knights who've taken it upon themselves to rescue me from my would-be verbal assailants. Of course, I'm not offended by this, either, because I know that they really don't mean to denigrate and infantilize me. It's just an unintentional side effect, no one's beyond that, and besides it's really not that big of a deal anyway. I should know.
I also deny the victim's et friends and family of victims' attempts to dictate to me what language I can and cannot use, whether through coercion, or shame, or force, solely by virtue of their narrow shoulders. Words are feeble vibrations in the atmosphere, or spots on a page, or pixels on a monitor. The only power they have over us is in the power we choose to give them. If it takes the individual's interpretation for them to do harm, and not every individual is necessarily harmed, then the point at which they become harmful has to lie in the listener. If you're so emotionally unstable that you cannot bear to hear mention of certain words and phrases, you are the problem; the rest of us are not obligated to expend effort on your behalf. If the wherewithal to escape this is beyond you, seek help. The rest of you, get a hold of yourselves and do try to exercise a modicum of self control.
I acknowledge there is a degree of desensitization to the plight of the marginalized in basing insults and insensitivities on their experiences, however this should not be mistaken for causation, and I remain unconvinced its effects aren't severely overshadowed by those original causes. Gaining two pounds when you're already obese isn't going to send you careening over any clearly defined edge, and there exist much better places to focus your good intentions. Unfortunately, they require slightly more time, effort and money than persecuting people who enjoy off-color jokes, so that may beyond the scope of the would-be messiah.
And in the end, we, too, inherited this cold and indifferent world.