“”Then how do you explains relics?”
Veneration. It can be explained by those Protestants I have seen openly weeping at The Church of the Nativity in Bethlehem, The Church of the Holy Sepulchre in Jerusalem, and the site of Jesus’ trial and scourging at the location believed to be Pilate’s Praetorium in Jerusalem.
Peace be with you”
For some it may simply be veneration. But even that comes dangerously close to worship. I don’t challenge the inclusion of art or crosses in a church, but many churches don’t have them simply to avoid anything even close to idol worship.
As for other protestants, some will fall into idol worship. I don’t call the emotional experience of weeping at the Church of Nativity idol worship, but God will judge their intent.
Symbols are powerful and useful. That is why the Nativity Scene is so popular, as is the image of Christ on the cross. But symbols are also dangerous when misused.
When you really hit the books in studying Catholicism you learn that the early teachings of the Church regarded religious art, especially icons, as actual windows into heaven through which we can project our senses and perceptions. Although some early Christians went so far as to believe that the icons formed a two-way portal between this world and the next that has never been Church teachings.
Peace be with you.