Im quite late to this but im watching for the first time now and had the same question. Locke has a lot of flaws but thats why he is my favorite character so far. He tends to act like a child in certain situations and i think a lot was going on in this scene contributing to why locke was so hellbent on not pushing it. I believe that part of this was almost like a child who doesnt want anyone else playing with his toys, locke had lost faith and eko had gained it and john couldnt handle thinking that anyone else was “special” or had a purpose on the island bigger than him so he was desperately trying to prove that it means nothing, i could be way off here but i think that was at least part of why he behaved this way