bcause he doesnt know that RS can stimulate and expose his potential thats why on previous chapters he keeps wondering why he felt strange with his body. later on when exo activated finally he found out that it was all bcause RS his body changed. that's why he break it.eventho being invisible is almost equal to find all blue to him, he still crush the RS because he doesnt want related to germa.
sanji doesnt want exoskeleton nor RS, he clearly hate it when it comes related to germa, but we couldnt blame him, it is in his blood, being strong.like it or not. sanji isnt even fighter on the ship lol, that's why we never seing him training combat, intelegent or combat ability during the series.because he isnt a fighter, but even with all those handicap, he still ends up matching zoro who spent his life devoted to being strong lol