Technically wouldn't the Kadets be the extremist party here given that they are proposing an extremely radical restructuring of the political and economic institutions and ideology that have governed the Soviet Union for almost a century and would necessitate a massive roll-back of the countries democratic institutions to fulfil? To say nothing of their chauvinistic dog-whistle politics with regards to Russian nationalism.
There is a reason why I called welfare "benefits" and made use of some insistent terminology.
The Kadets have also had historical issues with racism, anti-feminism and some absolutely virulent queerphobia (to this day they're against Transperson recognition, using "we want to help mentally ill people" dog whistle politics) which while better by the 2010s, still means their voting base is majority white, male, and Russian. And not a particularly big slice of white male Russians either as they want to completely dismantle the Soviet government's council and syndicate based democracy for some largely incompatible Bourgie representative structure as well as cut social benefits massively.
And their schemes for instituting western European style gun control and somehow destroying the millions upon millions of firearms in militia or personal hands are fantastical at best.