A District of Columbia judge ruled that JAMS is shielded from a breach-of-contract suit filed after one of its former mediators, a retired Cook County judge, mass-emailed a racist blog post to one of the attorneys in an arbitration case before him.But the judge wouldn’t dismiss the National Rifle Association’s unjust enrichment case against Winston & Strawn — the opposing counsel in the arbitration gone awry — finding the gun group sufficiently argued the firm should have disclosed a relationship between the …