How would I translate the two morphemes 基腐 together?
I don't believe an established, succinct English translation exists yet. I would try to translate as 'BL &amp; Fandom' or 'BL &amp; Fans'. 

For 基, I would prefer to use words like Boy Love/Yaoi over gay/homosexual to convey the romantic and fantasized view of male homosexual in 腐 culture. I also couldn't find any better translation for 腐女 than BL fans. Hence 基腐 can be shorted to 'BL &amp; Fans'.