Lebanese "Marxist" & exposed British military collaborator Gilbert Achar just accused Ansarullah/Houthis of being "an ultra-fundamentalist sectarian group" after a long history of defending so-called "revolutionaries" that became al-Qaeda & ISIS, and after cheering the NATO invasion of Libya on behalf of those same forces, with no sense of irony or embarrassment, which is an achievement in itself.
What does "fundamentalist" even mean? The civilisational history of Islam following the death of its prophet has always been deeply divided by civil wars over the essence of the religion. The Islam of the poor was always very different from that of the rich, and thus the Islam of the state frequently clashed with rebellions also justified in the name of Islam.
On one end of the spectrum there's Ahmad ibn Hanbal, al-Ghazali and Ibn Taymiyyah who all argued that an unjust status quo is preferable to the anarchy that would likely follow its overthrow, whereas on the other end of the spectrum, there are the Zaydis who argue that Muslims have an obligation to rebel against unjust and corrupt rulers.
Saudi Arabia is favourable to the "quietism" of the former sort, whereas the Yemeni national resistance led by Ansarullah are Zaydis, who far from being "sectarian" are more accurately the bridge between Sunni & Shia in the sense that they accept the legitimacy of the first three Caliphs (proto-Sunni) while reserving their preference for Ali (proto-Shia), and therefore, they are sometimes referred to as "the Sunnis of the Shia, and the Shia of the Sunnis".
Somehow this makes them "ultra-fundamentalist sectarian" according to Achcar, but what on earth does that even mean? Ansarullah was founded in the 1990s as an indigenous response to the Saudi-Wahhabi'isation of Yemen in the 1980s when the country was being used as a recruiting ground for the US-Saudi-Pakistani "jihad" against the Soviet-backed socialist government of Afghanistan, Bin Laden was himself Yemeni.
Following the Soviet collapse, the pro-Saudi Yemeni government of Ali Abdullah Saleh first crushed the Yemeni Socialist Party that ruled South Yemen with help from returned al-Qaeda mercenaries. Back then the founder of Ansarullah, Sayed Hussein al-Houthi, sided with the persecuted socialists, because for him the real enemy was the unjust and corrupt Saleh government, not the "infidel" Marxist-Leninists.
The record shows that Ansarullah never took up arms against the state, rather the state, urged by Saudi Arabia, took up arms against them, first by assassinating Sayed Hussein al-Houthi in 2004, and once again relying on al-Qaeda mercenaries drawn from across the world to wage the Six Sa'ada wars (2004-10) against them. In typical Shia fashion, persecution only made Ansarullah stronger to the point where the state defected to their side in September 2014, that is, the so-called "Houthi takeover" that triggered the Saudi aggression in March the following year.
This revolution was relatively bloodless because it was popular. Unlike the so-called "revolutionaries" in Syria, Ansarullah did not need to import mercenaries from across the world or rely on billions in funding because they actually did manage to convince the bulk of the Yemeni army that they were acting in "the general interest of the homeland" to quote the Interior Ministry.
Yes, Saleh tried to opportunistically join the revolutionary bandwagon but when he tried to change sides and join the Saudi aggressors, he was killed by the national resistance in December 2017, but it made no difference to Ansarullah's power because Saleh was discredited and unpopular anyway.
For throwing off a pro-Saudi status quo that kept the country an impoverished source of cheap labour and mercenaries for the US/UK backed Gulf monarchies, and for asserting its independence of which it was robbed following the 1977 assassination of President Ibrahim al-Hamdi (most likely instigated by the Saudis), the Saudis have turned to genocide.
Even the Australian commander of the UAE occupation of Yemen, Mike Hindmarsh, referred to Ansarullah as the "Yemeni Viet Cong", because despite being a war-criminal, he's more honest than the "Marxist" Achcar who's reduced to spouting cheap Saudi propaganda.