Western civilization at least is currently of the opinion that heritable political power is net bad, even if there are plenty of examples of it being good. I suspect the primary reason for this is that competence, context, and experience aren't easy to pass on to your children, and most of the things that make an individual worthy of wielding tremendous power get lost and corrupted after only 2-3 generations.
Most of us can agree now that Chouinard is probably doing net good for Earth's biosphere. Why do you think that will continue to be the case when his grandchildren and great-grandchildren are in charge? Even if they still have the same surface level values, how do you know that they won't be so under educated and incompetent that they won't make counter productive and even destructive decisions with the unearned power they have?
I have zero problem with competent and successful individuals who become absurdly wealthy and powerful.
I have many problems with these individuals then attempting to pass on their extreme wealth and power to their offspring who almost certainly aren't strong enough to wield it.
You raise excellent points about perpetuating lineages and yet your proposal would immediately put a large portion of patagonia in the hands of the very people you propose to want to keep power away from.
If we get another nike or adidas in 2 generations instead of as soon as the guy dies, that's still a way better outcome.
Not to mention that the reason the family is receiving said tax break is because the firm's income will no longer flow through them. Giving up the future profits of the firm in perpetuity is surely more expensive than paying a one-time tax bill.
It is symptomatic of our society that people find it impossible to believe that there is even one wealthy man on the planet whose goals and actions aren't entirely self-centered.