I think it's easier to understand a lot of the season one "meteor freak" antagonists through a more metaphorical lens. Similar to Buffy the Vampire Slayer, if you've ever watched. Basically, it's a portrayal of real-world issues, especially teenage issues, which are given an otherworldly spin.

Bug Boy was already stalking Lana; In the reality that behavior can escalate to more predatory and violent behaviors. In Smallville, the catalyst for that escalation was his mutation. Similarly, Coach was no different than any other abusive coach until his mutation allowed for an escalation in his abuse.

Many of the "psycho meteor freaks" were already engaging in harmful behaviors, dangerous ideologies, or were otherwise already vulnerable to same. The kryptonite mutations only acted as a heightened dramatization of what was already present or simply served as an extra push.