Homeschooling conventions are not necessarily Christian or Biblical. The comprise of all varieties of ideologies, some which would be incompatible with AIG.
The board of this particular homeschooling convention is
exclusively Christian, Biblical,
and YEC, and say that they "largely share AIG's perspective". But obviously not "largely" enough.
From their email to Ham:
After much prayer and deliberation over the weekend, Great Homeschool Convention's Advisory Board has unanimously decided to disinvite Ken and AIG from all future conventions, including the Cincinnati convention next week. The Board believes this to be the Lord's will for our convention and searched the Scriptures for the mind of the Lord and the leadership of the Holy Spirit before arriving at this decision. [...] Please know that our Board is 100% young earth and we largely share AIG's perspective from a scientific standpoint.
Edited by Dr Adequate, : No reason given.