I think you were right in raising a flag on that comment, but you should have went with "rude or offensive" instead of "not constructive". I think a rude or offensive comment is worse for the site than a non-constructive comment. So if you took offense, I think it would be more appropriate to use that flag instead. Being rude is never constructive, so "rude or offensive" is actually more specific than "not constructive". I mean, assuming that you took offense.
On a side note... I don't mean to start an argument about who started it, but your own comment probably also came off as rude. I mean, lmgtfy on a new usernew user seems really inappropriatereally inappropriate.