"When I was in my early twenties on a trip to East Africa, I saw a gazelle giving birth. It was truly amazing. Within minutes, the baby was standing up, standing up on its own. A few more minutes, and it was walking; and before I knew it, it was running alongside its mother, moving away with the herd. Humans aren't like that, Ambassador. We may come from the same planet as those gazelles, but we're pretty much helpless when we're born. It takes us months before we're able to crawl; almost a full year before we can walk. Our deep space mission isn't much different. We're going to stumble, make mistakes - I'm sure more than a few, before we find our footing. But we're going to learn from those mistakes. That's what being human is all about. I'm sorry you can't see that. "
Well, it's an entire speech, not a line. Why is it "bad"?
Well, first, in the episode where it appears, the Vulcans are trying to get Earth to recall Archer on the grounds that his operational recklessness set off the atmosphere on Tinder Box Planet, killing thousands, while Archer's got the proof that it was Suliban or whatever did it. So, what he should be emphasizing is, the thing the Vulcans are (rightly!) outraged by was the sabotage of people trying to get Archer's mission cancelled and not any inherent idiocy on Archer's part.
Second, the argument amounts to, ``you say we're not competent to do this job, and you're right, we're not, so we should keep doing it in the hopes that maybe someday we'll become competent''. There is a sensible argument to be made out of this --- that one can't be fully experienced without the experience --- but it's made in a muddled way that only works if the speaker is trying to appeal to sentiment, which indicates that Archer isn't aware of who his in-universe audience is.
