They only need to quit the party and remain an MP as an independent as they were voted in by constituents, not party members.
Kyle was chosen when the party was under the leadership of Miliband, not Corbyn. No party has 100% agreement on 100% of policies. If the people of Hove had wanted a...
They can't represent the views of all their constituents though, unless all their constituents have the same view. In any democratic vote there will be winners and losers.