“nisht: We’ve had this debate before. Either way, not knowing all of the intricate details of Hilchos Retzichah does not make one evil.”
However, some who is OTD, or someone who belives that their feelings drive halacha would be likely to commit retzicha in the aforementioned manners. (Think about taking the heart out of someone before he is halachically dead to transplant into someone else).
Most poskim hold that removing a feeding tube is more than just gram retzicha (if there is even such a concept) it is retzicha biyadayim.
So it is not hard to see how someone who goes off the derech can be oiver on retzicha. Giluy arayos and avidah zara is upgeredt.
I is actually hard to understand why there is a poster who thinks that going off the derech is not a slippery slope to being oiver even the most serious aveiros.