They draw their figures from the Los Angeles Times Proposition 8 campaign donation records (which shows "Lassens Health Food" donating $27,500 in support of Prop 8) and SF Gate's database of Proposition 8 contributions (enter "Lassen's" with the apostrophe in the contributor field, and it lists Lassen's as having donated $3,000 to support Prop 8).
Urging locals to boycott Lassen's, the petition reads:
A huge number of local residents (of all backgrounds and orientations) don't want our money being used to promote discriminatory laws. We plan to exercise our freedom by not giving ANY money to Lassen's and by telling our neighbors why.
The open letter to Lassen's also reads:
If you ever decide you want to take real steps toward undoing this wrong, we're wide open to positive change, and we'd be thrilled to have a neighborhood health food store that we can support in good conscience.
As of late last night, the petition had 41 signatures.