I agree; my argument is that that means we should consider if there's a monopoly issue. We shouldn't write new universal rules to address behaviors that only work if you're a monopoly; we should determine if there's abuse of a monopoly going on, and if so, treat the monopoly as the problem to fix. Doing otherwise risks saying "well, the monopoly is OK, as long as you fix this specific thing", and even entrenching those monopolies further. (For instance, even if you believe that it's acceptable to mandate explaining every refusal to do business with someone, taking the time to explain policies to everyone is something that may in some cases be easier for a large company but prohibitively hard for a smaller one.)

If you're abusing a monopoly in a way that prevents other people from coming in and doing better than you, that's the issue, not the specific manifestation of how you're abusing it.