A couple of thoughts on this topic;
1) The meaning of words inevitably changes over time. Even if we were to magic up an international language standardisation policy (that worked) and make every word crystal clear and reflect the meaning of the concept the next day the system would be broken. Why? Because someone would used a word metaphorically in slang even when it was literally nonsense (e.g. "wow that's really cool!") or someone in an advertising department will coin an inappropriate but sellable name (e.g. "why don't we call our operating system 'windows'?) or an academic will discover something new and have to form a word that both appropriately describes the discovery but in a manner that is practical for communication (e.g. "Right that's decided, we're calling it 'antimatter'", "fine but I still think that it will just mislead people. We should call it 'composed-of-particles-of-opposite-charge-matter'".
2) As has been pointed out 'anti-' has more than one meaning. It can be used to indicate opposite (e.g. antisense oligonucleotide) and opposing (e.g. antibody).