"In the spirit of keeping this in good taste, i'll try to phrase this nicely" creates the impression that you would really rather say something nasty, because t

"In the spirit of keeping this in good taste, i'll try to phrase this nicely" creates the impression that you would really rather say something nasty, because that would be the correct thing, but instead you don't do this to be 'nice'. Basically, your original sentence, to a 'native' speaker, comes across as the opposite: "TIOBE index is really bad and I'd like to chastise you for bringing it up." If you truly don't mean to be snarky, a better approach might be: "from what I can tell (implying that you are not certain) the TIOBE index is not a good measure. Here's why I think this is the case:"