Sometimes statistics are skewed by coincidence. Evidence of blacks receiving more cards isn't evidence of racist activities. At worst it merely suggests that racism might have informed decisions, but it most certainly is not hard evidence as the article implies.

A statistical analysis of all of the fouls committed over a season, showing that black players were called for 14% more fouls than white players on average and received a disproportionate number of cards and ejections is, by any reasonable definition of evidence, evidence that suggests racial bias. It's not definitive proof, but it's not claimed to be. It's a miles better form of evidence than "Here's one example of a card that was given to a black player because he didn't know a rule." There were plenty of new non-black MLS players too, and their "misunderstanding" cards were included in this analysis as well.

It's important to find and combat racism wherever it may rear its head, but to want racism where it isn't or to fight a battle that likely doesn't exist is a waste of time and counter to the cause.

You've already decided that racism "likely doesn't exist here. How have you decided that? Shoving your hand in the sand over potential issues of racial bias because you, for no real reason, think it likely doesn't exist is orders of magnitude more damaging to "the cause."