As any political party's membership should come to the conclusion: There are lines and relevant divisions. Some issues and priorities should be placed above others and some put lower in importance--the only alternative is one faction of partisan politics getting their way, and that somewhat naturally gravitates power to the more extreme factions. The flipside is that those divisions can become too loudly condemned by those dug-in to power as a convenient way of creating a scapegoat or holding onto power.
For example, folks in either partisan camp in the US will point to their own party with criticism. Those on the further ends of the spectrum usually condemn the compromise (also labeled 'hypocrisy') or even betrayal that is settled on by the central areas, and those on the less extreme ends of the spectrum usually criticize the unelectability/extremism of the extremists. Running in the other direction, people more milquetoast criticze the extremism and unelectability of those more central.
Chief example of both in the US is the parties national states--Democrats, on broad level, currently have the issue of moderates criticizing the extremes with the likes of Manchin and Sinema either by pragmatism or principle objecting to more extreme stuff. Republicans, largely, have the more extreme or, at least, hardline and insistent end criticizing the middle for being sellouts and spineless.
(Course, there's also elements in the D party who criticize the center--'The Squad', Ocasio-Cortez, etc.--and parts of the R who criticize the further-right--Mitt Romney and that ilk.).
It's basically just a consequence of subjective political opinions themselves that punching nominal 'allies' happens, and where the line between those folks sit is a pretty individual judgement that would conform a bit to faction ideas (Communists are less liable to work with, like, neoliberals, than they are democratic socialists in a party. Ultra or racial nationalists less liable to work with neoconservatives than they are nationalist conservatives). Endless argument could be had.
Personally, I'd wish both sides were more prone to punching towards their respective extremes than they are--and that principally seems to align with the parties more long-term coalitions/power-centers. It'd be nice to see Democrats criticizing Sanders and The Squad and that general wing, but this seems to happen less because those elements still abide by the dominant party narrative often enough not to get the treatment that Manchin or Sinema do*. They don't threaten the 'central' powerplayers of the party as much.
Similarly, Republican criticizing is somewhat famously a mess of a fight with old powerplayers that 'made sausage' (Bush, Romney, neocons, even the LIincoln Project likes, etc.) criticizning the harder-right and on the other side a bit of a mess of different right-wing ideologies that also dislike one another criticizing the central power-players that, on a national level, is basically a holding-pattern fight until 2024 primaries settle things.
*Course, contributing to that is Manchin and Sinema having more influence/power as Senators than The Squad and most of the rest of the more hard left-wing folks. 'House' moderate Dems seem less common than the House extremist ones and that naturally drives some of the national focus.