I suspect that any fan that says that s/he wouldn't welcome Lebron isn't being honest with him/herself.
few legitimate reasons I don't want him:
1. As soon as he loses twice in the finals he looks for a new team
2. He quits games during regular season and calls it rest, causing team to limp into playoffs
3. That resting is going to get worse as he ages
4. A lot of his game will not age well. Ray Allen made sense playing old. But lebron style of play not sure
5. I'd rather beat him than join him. Like others said it doesn't feel good that the guy we couldn't get past for a decade joins us