Looks like most are happy with study showing the happiest folk in the world being found to be in such a nation so rife with happlesness and hopelessness.
I haven't noticed the others actually accepting the original interpretation or not. I think that your source got it wrong. But don't care enough to dig it out. The others aren't agreeing or disagrreing with the "happiness" of Nigeria. They are strongly disagreeing with bigotry being used as a reason for rejecting it.
My reading of what might be the original material is that Nigerians are, on average, the happiest on a
per GNP per captia basis. I see nothing very unlikely about that result. Especially when I step back and look at where other countries fall.