Old Matador & Bull In Ring Oil Painting Signed RJG - AJG

Old Matador Bullfight in the ring Oil on canvas Painting signed RJG - AJG.
Picture is very large 36" or 3ft long X 28" or 2ft 4 inches. This painting is at least 100 - 150 yrs old due to the cracks in the paint, at the moment I am thinking of getting it restored, due to I can not touch it without the paint falling off. Bullfighting traces its roots to prehistoric bull worship and sacrifice, but it is not everyone's cup of tea due to obvious reason of cruelty to the bull. I myself think it cruel and would not pay to watch it as I love animals, my best friend is my dog patch who never lets me down like friends can do. Anyway back to the picture it is not in the best condition but easily repaired. I like this picture even though I don't believe that the actual sport of bullfighting is right. Due to the subject does this decrease the value of paintings or does it increase their value? Also does anyone know who the artist is? I have uploaded a picture of a gallery stamp on the back but as you can see it has faded away due to age. I purchased this in a house clearance so it owes me nothing.