Even though people will likely die in the future because of unexploded ordnance, more lives could be saved if Russia loses sooner because of cluster bombs.
The difference is that Ukraine will keep a detailed record of where these bombs will be used, thus helping to prevent many future casualties that would surely occur otherwise.
tl;dr: If they can dish it, they should take it.
Since the start of their full-scale invasion of Ukraine, Russia has been using banned cluster bombs and banned white phosphorous on Ukrainian civilians and military alike. This is in addition to all their other violations of international laws, the Geneva convention, and human rights.
Respect for international law and human rights is a two-way street and if one side violates them then they lose under protection under it. Anyone seeking to protect Russia under international laws & human rights after Russia has been violating them is either one of Putins useful idiots or his agent.
Russian use of cluster bombs : https://edition.cnn.com/europe/live-news/ukraine-russia-putin-news-03-04-22/h_31e4649324f51b1fe5df5a87d8082edd
Russian use of white phospohorus : https://www.nbcnews.com/news/world/what-is-phosphorus-bomb-russia-ukraine-rcna21371
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