Technically, web browsers can control what users see, and sites using Javascript can overwrite anything coming from the original authors. Browsers heavily utilize Javascript to create an interactive Internet; sites like YouTube, Facebook, and Gmail could be crippled without it.
Google is a private company. It has the capacity to utilize its massive power for whatever political agenda it chooses. But for it to pretend to be an advocate for Internet freedom while simultaneously disadvantaging messages it finds politically incorrect is deeply hypocritical.