There have been numerous examples of Donald Trump waving off facts, research, and data in favor of a theory that fits his world view better.
Climate change – with pretty much every country and almost all credible climate scientists arguing that there are human (and economic) impacts on the economy, Trump has argued that it either doesn’t exist or that it’s a conspiracy created by the Chinese.
His support for the Iraq war – with overwhelming evidence that Trump supported the Iraq war, he refused throughout the election to acknowledge his support.
Despite all of the facts pointing toward Russia’s interference in our election and attempting to tip the scale in his favor, Trump has steadfastly refused to take the advice of the experts who agree that Putin, in fact, ordered direct interference in the US election. While it’s tempting to try to understand why Trump will not acknowledge Russia’s role in the election (it could be his unwillingness to acknowledge that his surprising victory was due to more than his charisma) the most important thing to address is that a president who selects which intelligence findings he wants to accept is likely to make decisions based on bias rather than on intelligent and fact-based deliberation.
A strong president has guiding beliefs and values that, taken with the facts and data from the modern world, help his/her as decisions are made with advisers and other world leaders. The values that drive Donald Trump’s continued support of Vladimir Putin are divorced from fact. When Trump makes decisions that are not based on facts he has to answer questions about how he came to the conclusions he did.