A man identifying as a woman is one thing, but Caster Semenya is a naturally-born woman who happens to have different hormone levels than her competition. It's clearly discriminatory to force a human being to medically alter their natural body to compete in artificial standards of the gender category they were born into. The ECHR made the absolutely correct ruling.
World Athletics simply wants to ensure that the majority of women are given a fair shot in competitions. Unfortunately for those with medically-verified differences in sex development (DSD), their testosterone levels can be so high they breach the average levels seen in men — most women cannot compete against such advantages. The rules from World Athletics may seem harsh but they're fair.