One must be exceedingly desperate to use its flag as an indication that the European Union is founded on the Christian identity! A vision for the Christian identity existed and remains alive, but the European Union is established rather against this vision than adopting it, and the selection of its flag is not an exception.
The connection with the flag of the supposed Christian identity of the European Union comes mainly from Arsene Heitz’s assertions. Thirty years and more after the adoption of this flag by the Council of Europe (1955) and after it became the official flag of the European Union (1985), the man who most likely designed it revealed that he was inspired by the Bible and the Roman Catholic liturgical tradition associated with the Virgin Mary.
A myth develops around Heitz’s faith and the flag almost as a symbol of divine origin, which however won’t explain why, if this is the case, Heitz did not present exclusively the particular design, but suggested a multitude of flags until the relevant institutions selected what they wanted!
In any case our own issue —the relation of the European flag with Christianity as a source of the European identity— is not the investigation of Heitz’s intents and statements but the criteria for the final choice of the specific symbol, and above all the function itself of the flag, the impression, sentiments and reasons it actually supports.
First the most important: ignoring Heitz’s statements and the relevant mythology, will one have by the flag itself any impression whatever of a relationship with Christianity?
If the European Union, independently of what inspired or not Heitz or anyone who proposed a flag according to one’s taste and inspiration, really wanted to make a reference to Christianity, it would have selected something else but not this vague circle of stars or whatever symbol able to be used by any kind of a union in any place and any culture.