The main argument against consumption inequality is that it's suboptimal in terms of average happiness / utility / well-being. If I spend $1M per month and transfer $1k of that spending to someone who spends $1k per month, average well-being would increase.

In the US, the top 10% are responsible for 50% of consumption. This means that higher redistribution can increase the spending of the bottom 90% by X% at the cost of decreasing the spending of the top 10% by X% (assuming no decrease in total production).

Of course, redistribution has negative effects too, I don't know what level of redistribution is optimal.