first, li has had many meetings with foreign counterparts prior to his disappearance.Removing senior officials due to corruption is good, but removing Li Shangfu now is especially damaging to Chinese image in global stage. Not just cause he's China's defence minister, but because the US can claim "He didn't meet with us because was always under Chinese investigations".
more importantly, you have just iterated another great feature of the Chinese system, which is its ruthlessness. if someone has got to go, he is gonna go regardless of how it looks to "the global stage".