The "how" sounds to many like some complicated and theoretical question from a constitutional law seminar, c. 1920. Not so. The "how" of things in government matters intensely and immensely. That is to say, does the end justify the means? Does it matter how we do things, so long as the things seem to us, broadly speaking, desirable and good? Or does the use of bad means impeach the whole project? We have here one of the great enduring questions of life, never answered entirely to the satisfaction of either side in a given dispute.
Judge Vinson's answer is the answer a earlier generations of Americans would have recognized as more fitting than the alternative. It would not have been for these generations a case of finding the purchase mandate evil, barbaric, anything like that. For many, it would have been a case of doubting whether, if Congress can tell you to buy a thing you don't want, any justification exists for calling ours a government of limited powers.
The Constitution was written and ratified by men who saw it as a means both of enabling and restricting government -- balancing the requirements of efficiency and freedom. On and on, the warfare has gone between those complementary yet competing concepts.
Since the New Deal, the general idea has been, yes, if Congress wants to do something (e.g., tell farmers what crops they may plant) for the supposed good of all, then such a plan must be good for all. Mustn't it?
It's a bit late in the day, you may think, to reopen that immense and vital question, but sometimes the rule is better late than never.