Deleting model from scene

Question

I'm trying to make a script that opens the .obj files from a folder one by one and performs a boolean operation based on an .stl file called rail.stl. Then I want this script to transform the .obj file into .stl before closing it and continuing with the next file inside the folder. In order to achieve this, before transforming the .obj into .stl, I want to remove the file rail.stl from the scene. This is what i'm trying and it's making blender crash every time I run it.

[...]

        # Import the "rail.stl"
        print(f"IMPORTING RAILS!")
        bpy.ops.import_mesh.stl(filepath=modifier_file)
        # Catch the modifier object inside modifier_obj
        modifier_obj = bpy.context.selected_objects[0]
        print(f"IMPORT FINISHED!\n")
        
        # Apply boolean modifier
        print(f"APPLYING BOOL MODIF {index}!!")
        for obj in bpy.context.scene.objects:
            if obj != modifier_obj:
                bpy.context.view_layer.objects.active = obj
                bool_mod = obj.modifiers.new("Boolean", "BOOLEAN")
                bool_mod.operation = 'DIFFERENCE'
                bool_mod.object = modifier_obj
                bpy.ops.object.modifier_apply(modifier=bool_mod.name)
                
                objects = bpy.context.scene.objects
                # Loop through all objects and delete the ones that are not active
                for obj in objects:
                    if obj != bpy.context.active_object:
                        bpy.data.objects.remove(obj, do_unlink=True)
        print(f"MODIFICATION FINISHED!!\n")

Then Blender is crashing when it gets to the line bpy.data.objects.remove(obj, do_unlink=True)

Is there any other way of closing the file rail.stl?

Thanks!