This argument concludes/recommends/argues that...
To support this conclusion the writer cites.../points out that...
However, this argument suffers from several critical flaws and is therefore unconvincing/ unpersuasive as it stands.
One problem with the argument is that, the editorial observes a correlation between... and..., then concludes that the former is the cause of the latter. However, the editorial fails to rule out other possible explanations for... For example, ... Any of these factors, or other social, political or economic factors, might lead to... Without ruling out all other such factors it is unfair to conclude that...
In the final analysis, the letter's author fails to adequately support the recommendation that... To bolster the argument, the arguer must provide detailed demographic/statistical evidence showing that... The author must also provide evidence -- perhaps by way of a reliable survey -- that...