I can imagine that we might refuse those particular offers from the Russians. They'd be in danger of being shot by the crazies. I actually read about the offer at some Russian-related site, but it didn't say that the offer had been refused.
Turning down the special forces team I can see. That would be a match in a powder barrel with the gangbangers down there. That article (nor any other) didn't say the rest of the Russian offers were turned down, though.
I did note that Sri Lanka isn't the only low-GDP nation that offered. Honduras, El Salvador, Jamaica, Hungary, Colombia, Dominican Republic -- none of those are what you'd call economic powerhouses.
My especial gratitude to all of them.