Explicit?, implicit? If atheists say that they can offer good things like charity, or that it is only when abrahamic faith is replaced by people becoming atheist that we can improve the lot of humanity then that is motivation by atheism.
Do you have anyone making that claim? Of course atheists are capable of charity, everyone is capable of charity. I'd argue that it's as impossible to justify charity BECAUSE of atheism as it is to justify the systematic murder of millions of Soviet citizens BECAUSE of atheism.
By contrast, there's any number of people out their using their religion to justify charity, but also to justify homophobia and racism and sexism and nationalism and all sorts of other despicable issues.
So, again, atheists are exactly as capable of showing any behaviour you'd like to come up with as anyone else, but can you show why you think their atheism has anything to do with those behaviours?
Ergo, if the Atheist community of Austin make an excuse that they haven't had time to chalk up as much giving as say the Catholics, then they haven't had the time to dish out the bad stuff.
If you have issue with something someone else somewhere else has said take it up with them.
O.