For example, you can widen the diversity of your applicant pool by reaching out to the groups you want to increase. If a company makes sure to have a booth at the major Society of Women Engineers job fairs, is that discrimination? Men are only being hurt in that there are more people applying for the same positions.
As another option, one could argue that there is a societal imbalance in the development of the talent pool, and attempt to correct that. If a company puts effort into encouraging women to go into engineering and, as an outcome, their pool of qualified applicants is more diverse, is that employment discrimination?
What I'm saying is that a company can put effort into expanding the diversity of their employee base in ways other than strict quotas and hiring discrimination, and without lowering the standard of the employees they hire. Is that really so bad?