I'm sure that tossing the putter in the air is a natural reaction (clearly it is as it's been done a million times), but couldn't Tiger's fist pump be his natural reaction? One man's natural reaction of joy is another man's taunt...
I guess the main thing is *a* reaction. Tiger's seems as natural as any and is more like what I'd do (maybe because I've seen it done more often than the putter flip, particularly since Tiger's won with such regularity), while the Nicklaus putter flip was his instinctive reaction. I don't see a problem with either.
And Tiger's not the only one pumping fists...I've seen more players do that than the putter flip in recent years - even on the Champions Tour.
Debating the merits of natural reactions - all of which stop well short of inappropriate levels in my opinion - seems a bit pointless in the end though, don't you think? I really doubt Tiger is intending to taunt other players when he pumps his fist, just as I doubt Nicklaus was trying to wound his competitors when he flipped up his putter, it's just all about being overcome with joy for a moment and letting it out.
The only golf course equivalent I can think of to match your comments on football would be spiking the flagstick, but I haven't seen that done yet!