Insults slipping through the diglossia filter

I recently came across a video, apparently from the little town of Souani near Tlemcen, of a poet, one Mohamed Tlemceni, performing a public satire of various Algerian establishment figures: كلمة في حق العصابة من إعداد شاعر الحراك تلمساني محمد. The poem itself is in Standard Arabic (Fusha), the normal language for formal public performance, but he intersperses elements from Algerian Arabic (Darja, italicised), as in:

أنتم تعيشون ببركات فخامته
فانحنوا له طاعة وامتثالا
خسئت يا من عرفناك رخيسا
شياتا للفساد طبّالا

"You all live thanks to His Excellency's blessings,
So bow down to him in obedience and compliance" -
Be off with you, you whom we know of old for a cheap bootlicker (lit. shoe-polisher),
a cheerleader (lit. drum-beater) for corruption!

or (in a reference to Ali Haddad):

جمعت ما يفوق الثلاثين مليار دولار بعرق جبيني
ولم أكن يوما محتالا
أول حرّاڨ بعد الحراك المبارك
فبعد أن كان ميليارديرا صار بطّالا

"I amassed more than 30 billion dollars by the sweat of my brow,
and was never once a crook."
The first harrag (illegal emigrant) after the blessed Hirak (protest movement) -
After being a billionaire, he became unemployed!

So what's going on here? The first part of the performance is satirical: for each person mentioned, he gives one or two vainglorious lines sarcastically put in the mouth of the target (often alluding to real quotes), then two or three tearing him down (then he throws the target's picture in the bin). In the second, he praises the Algerian people and urges it to ever greater achievements. Every single Darja element he uses is in the satirical part; various insults (shiyyat "bootlicker", Tebbal "cheerleader", HeRRag "illegal emigrant", HeRki "traitor") and one direct quote (mocked immediately aftewards). The unironic praise is pure Fusha.

This is not a particularly representative sample of the protests, as the small audience and the rural setting should suggest; in its theatrical, rather bombastic style, it harks back to the public speaking of the 1960s or 1970s more than to any contemporary mainstream. The theatricality is obviously to some extent deliberate and even prized; it almost inevitably accompanies the polished use of a language learned at school and never spoken in ordinary conversation. But it also undermines the force of emotional epithets, making them seem a bit recherché. Shifting into Darja for insults helps to restore their immediacy, while adding a bit of comic effect to a moment clearly intended to provoke laughter (at, not with). But it seems the poet is not yet ready to allow that kind of everyday realism into moments of hope; for dreaming of a bright future, only artfully selected, formal words will do. By relegating the Darja words exclusively to the context of mockery, he strengthens the principle of Fusha as the appropriate language for proper speech even as he violates it by letting them into the poem at all. It's a long way from something like Anes Tina's equally contemporary El Cha3be Yourid, where diglossia is hardly even felt as a relevant constraint.