That strikes me as a pretty extreme reaction. If it's an issue you care about and you think it's a viable approach, you'd really withhold your contribution on the basis of a required email address?
It smells bad. If I'm not explicitly asking them to send me stuff, what are they going to do with it except send me stuff I didn't ask for, AKA spam. This particular project may well be an exception, but on today's internet that's a healthy reflex.
Because it wouldn't be the first time I'd have been bitten by making donations to organizations that kept begging for money through the contact information provided.
I have no idea if they plan to do this, but I suspect they might (otherwise why would they require an email address?) and the onus on them to prove they don't intend to do that. Claiming you want to do something good doesn't automatically win everyone's trust.