Objective things are easily observed and defined. "I know it when I see it" is most often used as a catchall for things the speaker doesn't like. "I don't like it, therefore it's X" where X is this "obvious" thing that "everyone" agrees on when in reality, it's not X, it's not obvious, and not everyone agrees. Like morality.
You keep asserting that morality is objective but fail to offer anything to support that. Let me introduce you to another philosophical idea, Hitchen's razor
. The short version is: what can be asserted without evidence can be dismissed without evidence.
I don't know, discussion I was having with @Levistus's_Leviathan
earlier seemed to be heading towards an objective sort of view, albeit hard to prove - science can be used to objectively measure what is good or bad for people's health and wellbeing - whether through foods, medicines, non-medical drugs, drinks, through to physical activities done or inflicted on, through obviously to extremes of mental and physical injury / death.
From there, I think we can then go to intent - someone injures someone else on purpose for enjoyment or because they felt like it - so intending to do objectively bad for someone's health to that someone just for their own selfish desires, could be defined as objectively Evil for humanity. Whereas if injuring accidentally, or injuring to prevent said person from harming other people, or perhaps injuring because that is what the justice system has prescribed due to actions that someone has done already breaching laws etc.
Of course what that means, is because it is often hard to determine what someone's motive may have been (much like in court cases determining what degree of murder a murder charge may be) it can be hard to determine if what they did is objectively Evil or not, but doesn't mean we can't describe what is objectively Evil as such.
The challenge this poses for Dragonlance, is while killing all the people the Cataclysm did is objectively bad for all their health, to say whether it was objectively Evil could depend on the motivation of the Gods in question - was it to prevent even greater suffering, if so then perhaps you would say not objectively Evil, or if it was, whether they were stuck between two objectively Evil choices if we determined that for humans that inaction when you know inaction will cause harm is also objectively Evil. It comes down to how we would determine the motivation feeding into Good / Evil part.
All these considerations, and hard to escape the view that it all still is somewhat subjective, is why I could support the idea that there is objective Good / Evil for humanity - inasmuch that there isn't a cosmically objective Good / Evil - and aliens et al could have a different 'objective Good / objective Evil' as allows for possibility that for humans that eventually we could as a combined 'society' for want of a better word define what is objectively Good and Evil for us, based on what is objectively good and bad for our wellbeing and the motives for actions people take that could support either outcome. Not something I think as a society we have determined as yet, but something we could determine in future. A philosophical point of view, but that is what the thread is about
Note - have attempted to capitalize Good / Evil where talking about the moral sense, whereas not capitalize where talking about good / bad in the more physical / mental sense, to try and separate out where 'good' is essentially using two different definitions.