I've heard this argument many times before yet I've never once seen a shred of evidence to back it up. I'm not sure of the situation in the US but despite dealing with hundreds of UK tech companies and conferences in my career, I can categorically state I've never once witnessed anything that could be construed as sexism.
The direct opposite. In the UK tech market there is almost a desperation to hire female staff. The handful of female devs I've come across are generally paid more than what a male with the same level of experience would purely because companies are desperate to cling on to the precious few females that exist in the market.
In my time I've advertised over a hundred dev vacancies. I can honestly count on one hand the number of female applicants that applied.