@Cerberus. This has all become rather disjointed, so I’ll try to summarise.
The hypercorrection argument runs like this. Those who use ‘I’ where many of us might expect ‘me’ do so because they have had it drummed into them that they mustn’t say things like ‘Me and my brother went fishing’. As a result, they tend to avoid ‘me’ altogether where they have any doubt, thereby suggesting a degree of insecurity in their use of the first person personal pronoun in certain contexts.
This argument seems implausible to me, given the number and nature of the people who have used and use constructions…