It depends, if the subject is something like Sickle Cell Anemia, for example, then the context of requested participants is understandable. Not enough information here to say this is discrimination or simply having a target audience and/or research group.
At my company they are sponsoring a series of events to call attention to heart disease “the number one killer of women!”. They acknowledge that it is ALSO “the number one killer of men” but the focus of the educational program is women’s health.
I loathe political correctness. It kills.