If people select efficient enough charities, the benefits might outweigh the damage of deadweight loss, and value destruction via higher taxes. The thing is, this charity tax doesn’t seem to guarantee donation matching, it just increases the likelihood hat people will donate to something.
Maybe I am being confused by ambiguity, but the situation I imagined was that the government increases income tax between 1% and 10% and that the pool of money generated by this is given back to people who donate as a tax credit. If I donate $1,000 to AMF, I get $1,000 back from the government: but no guarantee that others will donate to AMF.
During the policy comment project by the UMD effective altruism group, we found that in some government agencies there actually is a degree of cost effectiveness analysis and meritocracy. This leads me to expect that the government will do slightly better than the population at deciding where to give in a more direct manner. The government is less likely to actually go through with something like the ALS ice bucket challenge, but when you have this sort of tax system it seems to me that such things might get economically damaging levels of funding, and that this will discourage future donations and charity in general.
Effective altruism needs to be much more popular for this tax idea to have a chance of being a good thing.