I'm not sure if I qualify as leftist, but I can answer your questions. Is there anything that makes me accept that leftists plicies are bad? Yes. Evidence, like Venezuela's example, prove that some leftists policies are bad. The current government and the policies it have taken are the only responsible for the current inflation and product scarcety. But that doesn't mean that every leftist policy is bad.

For example, the Venezuela government started programs to eliminate analphabetism, increased the number of doctors and free hospitals (in a program with the help of Cuba), reduced the infant death rate, increased the education budget, the access to potable water and other things like that. Granted, none of these measures are leftist per se, but also, these are not the things a right wing government cares about (at least not our right wing governments).

I think the reason so many people in Latin America is leftist is not ideology. It's simply that the other option is not liberalism, free markets and laisse faire. The alternative is chronism, medieval institutions (feudalism is alive in a lot of places), privatization of earnings and nationalization of loses.