There is nothing inherently wrong with the battle flag of the US Confederacy either. However some organizations have used it and thus associated it with specific ideologies that essentially everyone would agree is not good. The KKK using this flag is a perfect example. The symbol is now tainted because of this.
The V mask is and has been used by various groups who are doing things that we don't want to be associated with. Because of that, it is unwise and even detrimental to associate Ron Paul with the V iconology just like it would be bad to associate him with a Confederate battle flag.