This strikes me as extremely flawed reasoning, creating a false dichotomy between ${religion} and nihilism.
You don't need absolutes to exist in order for a concept to be meaningful. "Absolute Good" may be a contradiction in terms but that doesn't mean you can't judge whether something is good or bad (or make a more nuanced argument for why some aspects are good or bad in some ways). The same way as you don't need "absolute wet" to exist in order to judge whether something is wet or dry.
It's also a common parlor trick to talk about "evil" instead of "bad" as the antithesis of "good". Evil implies intent. But very few people would think of themselves as intentionally evil and take joy in that. Practically speaking "evil" is another way to say "sinful" and "sin" is a concept that only exists in religion because in most cases it describes genuinely "victimless crimes" as "crimes against God", specific religious codes of conduct that are imposed without a logical underpinning (e.g. "don't wear mixed fabrics" but also "don't kill people").
Religious morals generally don't care about good and bad, they care about adherence to a set of strict but arbitrary rules. Moderates in most religions pick and chose which rules are the "important" ones but they tend to base those decisions on social norms that have formed in the broader context their religion exists in, not some "inner truth" or unbiased intuition.
So in other words: "evil" is a distraction. It's how you perceive something but it says nothing about intent or cause. You can call someone an evil person, sure, but they don't get out of bed thinking "I'm so evil, I'm going to do a lot of evil things today", they just act in ways that actively harm people either out of disregard for other people's well-being or far more often out of a conflicting idea of what is or isn't harmful (or only empathising with a very narrow subset of the people they affect).