[GSlob]

See Hayek's "Road to serfdom". In his footnotes he touches upon the common genesis and more general commonality between fascism and communism. Indeed, their relationship is similar to that of 80 proof vodka and 190 proof Everclear. One could argue that the fascism is communism diluted.
Re: "You are aware that they are very distinct ideologies...? "
The purpose of an [any] ideology is behavior modification. What particular mythologies, symbols, slogans, ceremonials, texts and doctrines are used to achieve this goal, is of tertiary, not even of secondary importance. Essential [and not superficial] identity of ideologies is to be established NOT at the textual level or the level you refer to, but at the level of their "target behavior".

[forest]

Good explanation.