The basic rundown is that a country sets up international financing institutions, then loans money for infrastructure projects to less developed countries. This is supposed to be spent to hire engineering and construction companies from the lending country, with the promise that your companies will help up-skill the host countries favored companies, which may or may not happen.
The effect of this is that you basically use someone else's money to build up companies and build expertise that you can continue to sell around the world.
Its an obviously great business practice, but very prone to corruption, and ineffective at creating real economic growth in the host country (which is go-to cover story for why its not imperial aggression). The Belt and Road Initiative is basically just this exact strategy writ large.
Maybe he said something like "it looks like benevolent, because they use finance instead of guns" or that compared to using military force it's relatively benevolent, but after watching some of his talks, I highly doubt he'd call it a generous ethical policy.
Yellow man's burden?
Wars of aggression against two neighboring countries (Vietnam and India) in the past 50 years, active territorial disputes with basically every other significant country nearby. The creation of client states like which are then used to undermine stability (North Korea), or to undermine international organizations (Cambodia and ASEAN).
This is as expansionist as the American Civil War... I.e. it's not expansionist but really a 'domestic' matter.
There is big amount of propaganda from Western media on this topic as well: If Taiwan had been in a position to fight the communists to retake the mainland the US would have supplied help and call this 'liberation' of the mainland. But of course any plan of the communists to complete the takeover of the country by getting their hands on Taiwan is labelled 'expansionist' and 'a threat to security and stability'.
Same old games...
The Chinese government, the CCP and everything they stand for regarding liberty and freedom of thought and expression is against the fundamental values of the West. The ideas are not equal in value. China is wrong. Oppression of thought is wrong. Incarceration without trial is wrong.
The US and other countries don't get it right all the time, but at least our citizens have the expectation of rights the Chinese can only dream of.
Moreover, even if we accept that China is evil and wrong, some of the best 'friends' of the West are at least as evil and wrong, if not more, as China, which should really finish off this line of argumentation.
This is self-interest among states, standard geopolitics, there is not right or wrong, including when it comes to determining the US' foreign policy.