There are good reasons to attend another church. The most obvious is that you still want to serve God, but you realize that the witlesses are not the truth or cannot bear the bad treatment at the Kingdumb Hell. Another would be to disassociate yourself in lieu of writing a disassociation letter (or in addition to the letter).
Additionally, if one likes a portion of what the church does, one can join for that. You do not have to believe everything the church teaches--however, if you get benefits that exceed the total cost of joining the church, I see no reason why you cannot or should not join. Just make sure you know all the costs of being a member of that church before joining--go online, visit several churches, compare doctrines, ask what happens if you believe only 80% of what the church teaches but wish to continue going, and learn what is required for basic membership. Also, see how much pressure there is for advanced levels of membership (such as mentoring, missionary work, monastery style work, and the like) and if you are willing to do such if there is sizable pressure to do so. And, whether there is tithing requirements or whatever the total money contributions you are expected to make as a member.