Wow! Did you see that teenager run that stop sign? Teenage drivers are really pathetic.

This is just an opinion.

I have to agree with Dr. Bo in that until we know all of what prompts the two statements, we need to refrain from saying the person is necessarily reasoning poorly.   In a discussion with the individual, there's the opportunity to ask questions for clarification and understanding.  At the same time, if we're assessing whether the argument as presented is fallacious or valid, based just on what was presented in the one-liner, the argument seems to have some obvious flaws.

As I understand the argument, it goes like this:

Premise 1: One individual teenager ran a stop sign

Conclusion: Therefore, all (presumably) teen drivers are pathetic.

For openers, we seem to have some not-very-well defined terms, potentially leading to an ambiguity fallacy or perhaps even equivocation .  What does "run a stop sign" mean? ... drive through it at highway speeds or come not quite to a stop before moving through, or ... ?  Also, what is intended by "pathetic"? ... being of a very low standard or inspiring pity?  As well, there's the implication that there was no good reason for the driver not coming to a complete stop.

Also, there is the non sequitur of moving directly from failing to come to a complete stop to satisfying the requirement for being "pathetic".

Of course, there's an appeal to common belief, if we are part of a group of folks who believe teenage drivers are poor drivers.  There's a case to be made for cherry picking for taking one driving activity (performance by one driver at one stop sign) as an indicator of overall driving quality for all drivers of a particular class.

... but I digress ... the reality is that one does need more information and clarity before judging what the person actually believes and wants to say.

Still, like the "Can you Spot The Fallacy?" exercise we worked with a week or so ago, I found it interesting to see how many fallacies I could identify (even if I didn't get all the way through the alphabet! 😉) from a position presented in a fairly simply set of two sentences.

By itself I would say a hasty generalization. If you bring up statics I would say no.

Wouldn’t this be an opinion based on a non sequitur? 

“A teen ran a stop sign.

All teens are pathetic.”

implied: Get off my lawn!