Not even sure why something so self-evidently true needs to be argued. The time and resources spent on helping the disadvantaged by the very nature is not spent on the advantaged ones. Which means that they get less than they otherwise could have. Yes. And?
And that's without even getting into the morality of inherent advantage.
In the future. And even then, not necessarily. So for those advantaged it looks a lot like a forced investment of dubious profitability. Of course they oppose it.
> A rising tide lifts all boats
It has been shown several times that no, this doesn't necessarily work in economics, it is entirely possible that the rising tide will only lift the boats of the rich.
Directing resources to those already best-placed to use them is tempting, but taking it to its logical conclusion only perpetuates "the rich get richer and the poor get poorer." That, by itself, is a recipe for collapse over the long-term.
Again, without even touching on the moral aspects.
...to the same height.
Of course it is disadvantageous for some people to just rise with the tide.