A big part of it is that it's more aggrandizing and exhilarating to see yourself or your entity or alignment as "against the whole world", instead of "positioned in calculated opposition to certain things and somewhat aligned with the rises and falls of many historical formations", many of which take a whole lot of convincing and nuance because of how many pitfalls they fell for.

Someone really diving into an anarchist identity (not a meaningless liberal one) will either draw on histories of anarchists being suppressed or otherwise at odds with the USSR, or on much more recent queer and punk and insurrectionary authors who are critical of all party formations that seek to contend with governing atop entire countries. The latter will typically identify the CPSU as the most successful (fwiw) of these, and readily associate it with many modern-day communist parties, which they do have more of a direct experience of.

I am an anarchist - anarchists (as far as a monolithic ‘anarchists’ exists) do not hate communists. Anarchists are likely to disagree with some aspects of Marxist-Leninist ideology - they may even hate some aspects of it. But they do not hate communists - many of them would even identify as communists. Essentially all anarchists and communists share the same common end goal - a moneyless, classless, stateless society. Anarchists and MLs disagree on the implementation details - the best way to reach our goal.

The question as to why an anarchist would come to be in opposition to the ML approach for implementing communism - it’s not really about an “information source”, it’s just application of ideology. It would require the creation of a hierarchy. If the anarchist believes that hierarchy to be unjustified, then they will oppose it.

I couldn’t really point to any sort of individual source for my ideology. I came to realise over time that the one common thread that exists for all forms of oppression is power over others - wherever one group has held power over another group, oppression has occurred. If we want to prevent oppression, the answer emerges: get rid of as many imbalances of power as possible.

An anarchist knows that the risk of having a transitional state is that those empowered by the state will abuse that power to betray the people and the revolution. How likely that risk is, and whether it’s viable (or even possible) to achieve communism without a transitional state is the most important aspect which will define how (un)willing the anarchist would be to work with marxist-leninists.

Hope this helps, happy to answer any other questions you have about anarchism.