Different things are bad in different ways and need to be handled differently. You can’t functionally just go “both can be addictive and kill people therefore your argument is moot.” You’ve removed all qualifiers and context.

To compare them is to respond to a discussion on the threat of guns with some point about people weaponizing their cars and running people over because both can cause bodily harm. I think we can both agree that comparison strips all context and nuance from most conversations about guns OR cars and makes it difficult to talk about either in productive ways outside of the narrow/niche discussions.

TL;DR: this comparison spikes the conversation. Sugar and kratom do not present enough analogous health issues or enough of the same types risks to those around you to warrant lumping them together like that.

We're talking about dangerous substances you can buy OTC, and the health implications of those. Of course kratom and sugar fall into that bucket.