It seems you don't really argue to know that luck is or isn't the only factor. Which is really what I'm against. I'm against someone claiming he has proof of an answer, and he believes it is the full truth.
So ya, I think the danger part you're also generalizing a little. There are some people who telling them that luck isn't a factor is doing them a disservice. Like people who have been unlucky. There are a lot of people who try and fail. Why is that? It is not enough to work hard and spend a lot of time chasing success, that's why. That's the essence of survivorship bias. You must also be talented, smart, strong, tall, healthy, handsome, connected, etc. These things I argue you have or don't pretty much based out of luck. Out of everyone who tries, those who succeed will have either because of pure luck, like imagine everyone trying did 100% exactly the same actions, and it still ends up that only a fraction of those succeed, that would be pure luck. Or, it is the luck of what has caused you to beat the others, to think of better actions, and execute them better, to end up being one of the successful ones.
I personally think if our society acknowledged this, maybe we'd start thinking about society differently. Maybe we'd be more inclined to accept social programs. Instead of seeing everyone who is not a millionaire as lazy, and like it is entirely their fault. Maybe we'd have to come up with an organisation structure where maybe we don't have a winner takes most model. Or we'd need to recognize people's individual strengths, and make sure we find a way to make them helpful in those ways.
I see your point, and I actually mostly agree. I think it just depends who the audience is. If you talk to youths, obviously you should try to motivate them and ingrain into them a sense of having to work for success, and try to give them the smarts to do so. Also have them believe the effort is not wasted, and will make a difference in their life. But if you talk to people struggling to succeed, even after putting in the effort, I think you should also recognize that they can't be blamed entirely, a big part of success is luck. In the end, our society must find the right balance between the two.