Seriously?
First link: did you even read your link? Even the article admits that it is unlikely that diet soft drinks themselves are causing the increased weight gain; it is far more likely to be an epiphenomenon of the fact that people who drink greater quantities of diet soda are using it as a replacement for real soda when they are trying to lose weight, or trying to justify their unhealthy habits in other areas with cutting out sugar in soft drinks. None of the points raised cannot be minimized with prudence and forethought. And thankfully, even if he did not have it, he could count on (some of) us to provide it.
Second link: the only point it makes with even a modicum of validity is the one about aspartame. There is nothing about drinking diet soda that 'forces out' other beverages like water and tea, as the article claims. As for aspartame, I don't doubt there are some people that suffer reactions to it...just like how some people suffer adverse effects from eating gluten, or peanuts, or seafood, or chocolate, or drinking milk. This doesn't mean that nobody should ever eat any quantity of any of these foods, ever.
In regards to more serious, permanent side effects, generally these require far greater doses than is recommended by the FDA and than is generally consumed even by people who drink an excessive amount of soft drinks, given that, as the article points out, the stuff is 180 times sweeter than sugar. Trying to scaremonger on the basis of a few isolated anecdotal reports compared to several large meta-analyses and systematic reviews of the literature on the subject is pointless and intellectually dishonest.