Now, as the founder and developer of the smartsteem, I know that you can't check each and every post upvoted by your service, and I definitely know that you want to make steemit a better place and help people here.

Why not? Afaik they are only allowing people after reviewing their profile and content (to look reasonable). Every post can be checked but who is smartsteem to decide what should I see or not? Is this why we should abandon greedy centralized social networks?

Possible solution is shut it off unfortunately. It might sounds harsh but it's for the greater good. It's just a matter of time that another network/coin will be available for us without this kind of services. When it happens, all those stake-holder just going to watch us leaving one by one. Than they try to out-bit their own contents.