The largest group of internet users who use pseudonyms on the internet is probably women, and they do it because anyone with a woman's name on the internet is subject to harassment and stalking, and also because writing is often taken more seriously if it comes under a male name. So forbidding pseudonyms, whatever the intention, is sexist. Google's policy protects the abuses of privilege.
Google does not go to the expense of actually authenticating its users. They end up with names that their software accepts: not real names, but plausible names. Do not trust a Google+ name, regardless of Google's policies: such names are in no way trustworthy.
It is not just women who are harmed by this policy: it's everyone who is put at risk by speaking their minds under an easily-traceable name, or who is marginalized because of the use of their name. Police officers. Radio or television personalities. Closeted gay people. People with a violent exes. People who don't want their bosses snooping on them. Union organizers. Political activists at risk of their lives and freedoms.
Without pseudonyms, Salaam Pax could not have posted from Baghdad. George Eliot might not have published, and might have vanished without a trace if she had. Mark Twain would have had a different career.
The 800-pound gorillas in the room which everyone is ignoring is abuses on the part of US government security agencies, the data miners, the banking system, and the employment system. It's likely that government security agencies played a significant role in devising this policy, and the data miners that are both major Google customers and themselves sellers to the security agencies.
"Peace is not the absence of conflict, but the presence of justice."