That's not a valid argument. At the end of the day, if Google wants G+ to succeed they have to draw the line on offensive profile pics somewhere. Regardless of where the line falls, there will always be people who think it should be moved in one direction or another. To just say "I'm not offended by this content, Google must be doing it wrong" is ignoring the reality of the situation and failing to contribute to the discussion on how the issue could be handled better.
I'll expand a bit on why I think they're doing it wrong.
When you choose to follow/friend/circle/whatever someone you are making the choice to establish a social connection with that person. Social connections are far too broad to police. I might want to be friends with someone because they make horribly offensive jokes. I might want to be friends with someone because they produce art that could be considered offensive to someone. I might be friends with someone who I like enough to tolerate their offensive side. Whatever the dynamics of that relationship may be Google has no role in its complexities.
The next problem is consistency. I can be way more offensive with words than I can be with pictures. If they want to successfully police people's relationships they will have to also delete anything I say that might be offensive to someone else even if they're not my friend and even if I'm making a private post. As a user I don't think I can possibly understand everything that might offend Google or the millions of users of Google+. That's a huge burden to put on the user. Do I really want to spend the time writing a post on Google+ that may disappear because someone I don't know finds it offensive? I don't think they're doing this yet but if they're choosing to go down this road they are taking the responsibility so they will have to someday. A middle-finger is a pretty low bar. Right off the bat you have to ban 'fuck' from all posts because they are the same meaning.
The solution is pretty obvious. Either hide the profile picture until you friend/circle/whatever someone or give users the ability to rate themselves which solves a variety of other potential problems. I have no problem marking my profile NC-17 or whatever the equivalent would be.
Of course it's Google's site so they can do whatever they want with it. Questioning Google's policies is like a can of soup having an existential crisis.
And we can choose to criticize them for that choice. Ain't free speech wonderful?
How about when your kid/elderly relative does a search on google and sees it?
If I believe my kid is too young to see that, I wouldn't let him search on Google by himself. As for an elderly relative, I'm pretty sure any of mine can cope with a picture of someone flipping them off.
Sure, Google can choose to do whatever they want, but those choices have consequences. This policy could have the effect of making people feel like they can't "be themselves" on G+, and cause a drop in participation. I'm not saying this particular incident would have that effect (MG Siegler appears to not actually care), but it could for other cases.
G+ is an international social network. It's interesting how you assume that what's offensive to a large number of people in the US (maybe 100M people) should be offensive to the world (7B).
It's not offensive to me. I'm all grown up now.