Is Varoufakis someone that should generally be taken that seriously? The last time I heard about him was during the election for the European Parliament, where he was pushing DiEM25, which seemes like a rather idealistic (in the unrealistic sense) movement full of attention-hungry personalities.

Varoufakis' comment on China isn't about China per se but rather an extension of his economic criticism of financial capitalism. He views China as patient investors looking for long term returns from infrastructure projects instead of short term returns from financial speculation, and he believes the former is "far more humanistic" than the latter. He even gave an example when he was the finance minister: He renegotiated a better deal for the port with China, but the deal was blocked by the Troika. It's not a comparison between finance vs guns, as we all learned after 2008 that finance can be as destructive as guns.