What fallacy is this?

I am trying to point out that putting kids on sex offender registries is a bad idea, and this guy says

Neither does you defending kids having sex when they don't even know what it means to be an adult. You may keep saying "No", but your actions speak otherwise. Yes, the system has flaws but you are in no place to point them out considering where you are going with this.

Except, I am pointing out that treating kids as adults when it comes to sex is a bad idea. This isn't me defending them having sex!

The argument presented by "this guy" in the quoted text contains several logical fallacies and elements of poor reasoning. Here are the main issues:

1. **Straw Man Fallacy**: This occurs when someone misrepresents an opponent's position to make it easier to attack. In this case, the responder claims that you are defending kids having sex, which is a misrepresentation of your actual position. You are arguing against placing kids on sex offender registries, not defending the act of kids having sex.

2. **Ad Hominem Fallacy**: This is an attack on the person rather than addressing the argument. The responder states, "You are in no place to point them out considering where you are going with this," which dismisses your argument by attacking your credibility rather than addressing the merits of your point.

3. **Non Sequitur**: This occurs when a conclusion or statement does not logically follow from the previous argument or statement. The responder's statement does not directly address your argument about the flaws of placing kids on sex offender registries. Instead, it goes off on a tangent about you defending kids having sex, which doesn't logically connect to the point about the registry's effectiveness or fairness.

4. **Red Herring**: This is a diversionary tactic meant to distract from the original issue. By focusing on an accusation that you might be defending kids having sex, the responder diverts attention away from the actual discussion about the appropriateness of sex offender registries for minors.

In conclusion, the primary fallacies here are the **Straw Man Fallacy** and the **Ad Hominem Fallacy**, along with elements of **Non Sequitur** and **Red Herring**. The responder's argument fails to engage with your actual point and instead misrepresents your position and attacks your credibility.

That's a straightforward strawman fallacy on the other guy's part. You weren't advocating for kids having sex.

By the way, discussing the morals behind sex offending is very difficult, especially on the internet, and particularly when it concerns children. It brings out extremely strong, defensive emotions. People become combative quickly, and you'll often be accused of "enabling paedophilia" (or something similar) if you advocate for things like reforming offender registries. You'll have to decide if it's worth labouring the point or just cutting your losses.