I've seen the "I cannot say what is true becuase it gives strength to my political/ideological opponents" rationalization quite a bit recently.

My response has been simply that in this case, the individual has given up their ability to think freely. They are thought slaves, their minds being controlled by either (a) the groupthink of their preferred ideology, or (b) the necessity of being the opposite of the opposing ideology.

They no longer permit themselves to think rationally; their decisions are being made for them by others.