I would ask. ...
If there's a minimum standard of at least .500 for teams in "tougher conferences", what's the minimum standard for lesser conferences with "good conference records"? At least 4 games over .500 in conference play, 6 games over .500, 8, etc.? I don't think there can be a minimum standard for one (major conferences) without having one for the other (smaller conferences).
In my opinion, the way the tournament is set up now is more than fair to the smaller conferences in terms of tournament representation, and in its current format (68 teams) I would make that argument until the day I die; and I consider myself someone who doesn't mind championing a smaller school when their resume merits an at-large bid.
Basically there are about 10 conferences we can count on getting multiple bids in most seasons: ACC, A-10, Big East, B1G, Big 12, Missouri Valley, Mountain West, Pac 12, SEC, and West Coast. There are 31 automatic bids; take away the 10 I just mentioned and that still leaves 21 automatic spots going to the remaining conferences, despite the fact those conferences are nowhere near the same caliber as the ones in the upper-echelon. In addition, typically I'd say there will be another 4-5 at-large bids going to those conferences because a quality team doesn't win its conference tourney, for example this year it could be teams like Memphis (C-USA), Akron (MAC), Belmont (OVC), Middle Tennessee (Sun Belt), and/or Louisiana Tech (WAC).
So conservatively, that gets the typically "1-bid leagues" to about 25 or 26 spots, roughly 37-38% of the field. I think that's more than fair considering how inferior those 20 or so conferences are compared to the upper crust.