Well really, it's impossible to argue with this because it's entirely speculative, but I don't think there's much actual justification for it as an argument. IMO, Ponting has done more than enough on dicey wickets and against quality pace bowling to suggest to me that he'd be a great success in an era with top class fast bowlers and livelier pitches. To begin with, Ponting did actually have some measure of success against the quality seamers of the 90s. I just finished watching some of a mid-90s match where he made 88 against Ambrose, Walsh and Bishop in fact. He also made big runs against Wasim and Waqar and Donald and Pollock, and this is despite the fact that he was, frankly, a shadow of the player he is now when those players were playing. He didn't have a great record against the West Indies pre-2000, but he certainly had success against them and averaged 40 odd, while his average against South Africa pre-2000 was 49.60, and against Pakistan it was 63.20.
The main reason Ponting averaged in the low 40s in the first 5 or so years of his career isn't because he was dominated by these great pace attacks, but because he struggled in India, against England, and even against New Zealand. In other words, it was because he was a talented but inconsistent player and not because these bowlers had the best of him on a regular basis. As I pointed out in the above post, Steve Waugh had an absolutely shocking record for 8 or 9 years of test cricket, and was picked for his bowling half the time and averaged under 40. On top of that, that high 30s average was actually inflated by one really good series where he finally came good as a batsman before fading away again, in 1989. Despite that, it'd be absolutely absurd to suggest that the reason he didn't come good and become an all-time great until the mid to late 90s is because he couldn't handle the tremendous bowling of Phil DeFreitas and company in the late 80s and early 90s. It was simply a matter of when he matured as a batsman and when he made the necessary adjustments to his technique and shot selection to succeed, much like Ponting.
There is a valid argument that Ponting would struggle if he had to play all the time on slow, low turning wickets against quality spin attacks, but they didn't exactly abound in the 90s, and the argument that he'd struggle against Ambrose, Donald etc is a bit stupid because a) he didn't, and b) he's better now anyway. There's also the fact that Tendulkar (for example) has a lower average in the "easy" period where Ponting has been averaging 70+ than he did in the period where it is claimed Ponting would have struggled. Obviously this has plenty to do with the fact that he's declined as a player, but Ponting is written off for his pre-2001 average when was obviously not as good as he is now, which suggests a somewhat different standard for the two players.
My view is that people take a rather rose-tinted view of Tendulkar and Lara because they are the greats of an era which is currently viewed as a golden age of cricket. The reality is that like all players they made more runs in easier situations and against weaker bowlers than they did in more trying circumstances, and while their achievements are significant I don't see any particular reason to believe that modern players aren't capable of similar things. Lara is certainly the most dangerous of the four in my view when he gets it right, but I'd take Dravid for consistency against a variety of bowling attacks and in a variety of conditions, and Ponting in a pressure situation or for reliability against quality pace bowling in general, and both of them pretty comfortably. Tendulkar is probably the best of the bunch against spin, though Lara obviously pushes him quite close in that regard and Ponting, while quite a good player of spin, is well behind the other three. Tendulkar is certainly the best ODI player of the bunch, if you take that into account, with Ponting probably second and Dravid last by a reasonable distance. Dravid and Ponting are still in the middle of their careers and that is a barrier to giving a conclusive reading of their abilities, but there's no doubt in my mind that all four players deserve the status of all-time greats, and when all of them have completed their careers I think they will be on a comparable level as batsmen.