Please note that Sparkpeople.com does not preview or endorse their advertisers. They don't even know WHO the ads are for! They don't sell ad space to each advertiser, they use an advertisement supplying company that sells the spots for them.
So they don't make the decision to "allow" each of the individual advertisers. :)
However, if you find some to be inconsistent with the site's goals, by all means report it! Here's what you do: www.sparkpeople.com/resource/motivation_ar
Just remember they don't preview and vet them first - so yes there will always be some ads that are not consistent with Spark's philosophies. They deal with them as and when reported.