'demonstrate ignorance' is correct and can be used in written English.
You could use it to talk about a situation where someone has shown lack of knowledge or awareness of something, typically in a way that is seen as not acceptable. For example, "The president demonstrated his ignorance when he commented on the international crisis without any understanding of the details."
A much worse, perhaps unpardonable sin, for a Conservative minister is to demonstrate ignorance of your own nation's rich heritage.
This straightforward description of a subtle and widespread problem greatly enabled by technology is a rarity in a world dominated by legislators and judges who regularly demonstrate ignorance on high-tech topics.
Bishop Jenky's comments demonstrate ignorance of history, insensitivity to victims of genocide, and absence of judgment.
They, as I have previously noted in my essays, demonstrate ignorance of the role of regional geopolitics, economic systems, and human rights in foreign policy.
However, mentalities such as these merely demonstrate ignorance of the ways that meaning and control are connected to the way that we linguistically talk about and attempt to understand one another.
His original confessions, for example, demonstrated ignorance of many aspects of the crimes.
"Criticism of the transition makes pretty soundbites, but demonstrates ignorance of what really happened," Aylwin said in an interview with the Spanish newspaper El País in 2012.
However, drawing parallels between the Woodland Trust's native woodland policy and xenophobia demonstrates ignorance of the ecology and the conservation of semi-natural woodlands.
To imply that a priest is like a shaman and a puppeteer, "who, before the eyes of his congregation, transforms the inanimate wafer and wine into the living flesh and blood of Jesus Christ," demonstrates ignorance.
Walker also noted that during the recent congressional hearings featuring the testimony of Facebook CEO Mark Zuckerberg, politicians demonstrated ignorance about the workings of social media platforms and of cellphone technology.
"Will AI be a lever for good, or simply compound disadvantages built into our systems?" Walker also noted that during the recent congressional hearings featuring the testimony of Facebook CEO Mark Zuckerberg, politicians demonstrated ignorance about the workings of social media platforms and of cellphone technology.
