This took place in context of Colby expressing approval for a proposal by US House representative Seth Moulton suggesting that the US blow up TSMC facilities in Taiwan to prevent them from falling into Chinese hands–ostensibly with the view that this would be a deterrent to military action by China against Taiwan. As part of the same remarks, Moulton remarked that Taiwanese are not exactly fans of the idea. Zha was retweeting a clip showing Moulton making these remarks. Since then, Moulton has claimed that the video of the remarks were edited.
For tankies such as Zha, circulating the clip was to suggest that the US is not a reliable ally for Taiwan and is only seeking to prop Taiwan up to counter China, but that it would be quick to abandon Taiwan in the event of war. On the other hand, Colby has made a number of outlandish suggestions about Taiwan in the past, including the argument that the US should economically sanction Taiwan to do more for its own defense–never mind that Taiwan already largely purchases its arms from American companies.
Certainly, the US is not exactly doing itself any favors when former US government officials or elected politicians propose destroying TSMC facilities. Such statements have been amplified by the pan-Blue camp in order to sow doubt about the reliability of the US as an ally. Indeed, most recently, this even repeated in the pages of the New York Times by Ma administration former Minister of Culture Lung Ying-tai.
To this extent, it is the case that the US backs Taiwan for its own interests rather than any abiding commitment to Taiwan. As recently as 2012, the US preferred that the KMT take power over the DPP, with the view that Tsai Ing-wen would prove a dangerous pro-independence provocateur in the mold of her predecessor, Chen Shui-bian.
But, of course, even if Colby and his ilk reveal their lack of genuine concern for Taiwan here, it is not as though Zha seeks any better. Zha here simply seeks to cast doubt about the US’s reliability because he wishes for skepticism about the US to set in in Taiwan–this would then remove one of the deterrents to China invading Taiwan, if Taiwan is sufficiently doubtful of the US that it does not accept US support.
What is needed in Taiwan, then, is critical views of the US that are realistic in nature rather than conspiratorial fear-mongering. The US backs countries for its own ends and can abandon them once it proves inconvenient to back them beyond a certain point. Nevertheless, while Taiwan should be keenly aware of this, it needs to have a realistic assessment of how this would occur–rather than giving weight to the deluded views of individuals such as Colby, Moulton, or Zha.
Minister of Defense Chiu Kuo-cheng has stated in comments that the military would not allow the US to destroy TSMC in the event of a Chinese invasion. Certainly, that would be an act of war. Colby, Moulton, and ilk likely do not realize that through such comments, they give ammo to the pan-Blue camp. Probably in the way that they seem to pay little attention to Taiwanese agency, it can be expected that they have no awareness of Taiwanese domestic politics. Yet one expects such comments to be leveraged on by the pan-Blue camp.