This is a facile analysis. If you believe HFT internalizers are taking money from retail traders, try to outline the series of orders that results in money from the retail trader's pocket going into the HFT's pocket, and precisely how the retail trader could have made that same money on their own.
The reality is that market makers price non-retail flow more conservatively (ie: costing traders more) because they have to anticipate informed large block trades wiping them out. Since they don't have to do that for retail flow, their cost basis for those trades is lower, and they can (and do) split the proceeds of that reduced cost with brokerages.
It's overwhelmingly likely that any other brokerage you use does the same thing, and simply doesn't tell you or pass any of those savings on to you.
The reality is that market makers price non-retail flow more conservatively (ie: costing traders more) because they have to anticipate informed large block trades wiping them out. Since they don't have to do that for retail flow, their cost basis for those trades is lower, and they can (and do) split the proceeds of that reduced cost with brokerages.
It's overwhelmingly likely that any other brokerage you use does the same thing, and simply doesn't tell you or pass any of those savings on to you.