Its not actually free...I'm sure BPS is donating the cards. The more members they have, the more potential donations and volunteer help they can get - and the more potential new members (referrals). Its all about supporting the only group who is supporting us. The more numbers we have on our side the better.
Before this mess, the NRA membership was a tiny fraction of actual gun owner numbers. They've gained a ton of new members in the past month, but at the end of the day...most gun owners still won't part with a puny amount of money each year to be a member, which in my opinion is pathetic. They could cut out mcdonalds 5 times a year and pay their dues.
My thought is...if you aren't a member, don't complain about a thing that goes on.