Somebody donating to a charity to reduce their tax liability isn't the same as spending time doing actual charitable work.
The latter tends to indicate the person has motivations which stretch further than personal financial gain.
So giving money in this circumstance has no value or is perhaps 'grey money' at best, giving time does? I suggest most of the people who run charities would laugh at such a suggestion.
As someone who has given time and money to various charities over the years, but also someone who legally manages his personal tax liability, how do you view me?