Passion breeds irrationality, fans of every team in every league on the planet discuss all kinds of stupid stuff on message boards. Look up Internet forums for any English Premier League club....it's hilarious, and makes this forum look like kindergarten.
I can only speak for myself, but Brown doesn't get as much flak from me as Richards does simply because Brown's effort is never in question. His execution is. Brown's contract is awful, he's a turnover machine, he'll probably never score 25+ goals in a season again, and his physical game is declining....buuuut, at least skates full speed out there. Consistently.
Richards gets more abuse since his decline is a matter of both lack of execution and effort. Terrible combo.