You left out an important word. The SC has held that an employer does not automatically violate the ADEA etc. As your own source continues: "Age discrimination

You left out an important word. The SC has held that an employer does not automatically violate the ADEA etc. As your own source continues: "Age discrimination may exist, however, where an employer terminates an employee based on a factor such as experience or salary where the employer presupposes a correlation with age and uses that factor as a proxy for age." That is in fact what ultimately happened with Hazen, by the way. The use of proxy criteria as a facade for discrimination has been addressed in many other discrimination/quota cases, and courts routinely see right through it. So the answer to your question is basically no, unless the employer can prove that they were more than normally oblivious to the disparate effect their choices would have. I don't think any of IBM's lawyers are likely to suggest such a defense.