Blogger: Can We Opt Out Google Plus Resource on Blogger?

As you can see

The plusone.js is a built-in resource for any Blogger blog. It can be only disabled by commenting out some widget tags on the XHTML which pull the built-in resources (CSS, JS, Analytics, etc).

But then, the widget.js will also get disabled.
Meaning all the Blogger widgets cannot run properly, or at all.

It "can't be removed" on front-end, namely, using JavaScript.
It can, the element can be removed, but it will be very late.
The resource will still be pulled in first.
Like, d'uh.

So the answer is, sadly, NO, we can't

It's a server side.
We hope Blogger team, one day, will consider to create an option to enable/disable Google Plus on Blogger.
One day.