Which is fair enough really. Both "it can be argued" and "some would argue" are wishy-washy phrases that people use if they're not sure who thinks that and to what extent it's a valid or widespread opinion. It comes across that you've thought of something yourself out of the blue, aren't confident about whether it's a new idea or not, imagine that some people have probably thought the same before, and haven't put in the effort to find out if that's the case or not. Instead you should be making it clear whether you're explaining other people's opinions (in which case you should say whose opinions they are) or have an idea of your own (if that's appropriate), in which case again you should say so, perhaps with explanations of how it agrees or disagrees with previous ideas and why in your opinion it is a feasible or reasonable opinion.