It’s not an urban myth it’s a western misanderstanding of slavic hystory (the part that embraces Tartar Yoke period). Somehow they think that Yoke means that slavs were raped from morning to evening. 
They just can’t comprehend that tartars mostly took money and burned villages only if they didn’t get money out of it. Slavic women were considered ugly. There are evidences that sometimes tartars even made contracts with local slavic dukes to make military assistance in submission of other local slavic dukes.