Diversity isn't a zero sum game. STEM is one of the fastest growing professional fields, meaning more people--of any gender--will need to fill those jobs.
The goal is gender balance, there's no need to fear that a woman or a person of color accepting a newly created STEM job will somehow push a white man out of his existing position. Let's be realistic here.
Perhaps, but I could take these arguments more seriously if western countries weren't so excited about issuing more visas for tech workers. It's also possible that we have a tech bubble that people are wisely avoiding.
For that to make sense you'd really have to believe that the US will need fewer, not more, STEM jobs in the future. The vast majority of educated STEM workers and engineers are completely removed from venture-funded Silicon Valley startups and any potential 'tech bubble.'
So those men who would otherwise be in STEM must move to other professions, which means they either move into other male dominated professions and make them even more unbalanced or there must be an equivalent push to move them into a female dominated industry.
If we do the latter then a possible outcome is a system where we are allocating people to jobs based primarily on demographics rather than interest or aptitude.