How can anybody defend supply side economics when supply exceeds demand?

What I don't understand is how people can defend supply side economics when supply exceeds demand. I mean just because the supply side of our economy has more money, doesn't mean that it's a good idea for them to invest that money in the market. And if they're smart they wont invest that money. At least they won't invest it in the faltering american market. If they don't invest it in the market, how can that money "trickle down"? If the money doesn't trickle down, then how can the bulk of american consumers increase their demand? If demand doesn't rise, then how will the market ever recover? Re-distribution of wealth is inevitable. Re-distribution of wealth is what drives the us economy. Whether its re-distributed through government action or inaction doesn't matter. But without a good balance of supply and demand as well as a healthy middle class, the re-distribution grinds to a halt. The american economy grinds to a halt. Honestly the only immediate and effective way to boost demand is to distribute a modest amount of money to the true consumers of this country. The middle to lower class off this country. I just don't see how people cant accept this is a valid argument. Please illuminate me if you find flaws in this logic.