I think the vote percentage should be (# in server-1) /2
Ie. 20 ppl in the server = (20-1)/2 = 19/2 = 9.5
9.5/20 = 48%
51% would require someone (atleast 1 or 2) on the other team to voteban as well. If it where 50% then everyone on the team (minus the hacker) plus someone on the other team would have to vote. Often times the other team may not be aware of the tk'ing (or may not care) and not vote at all.
Setting this variable in the server's config should be fine until the vote stuff can get sorted and/or implemented
Code:
// Kick players who team-kill within this many seconds of a round restart.
mp_spawnprotectiontime 10