No. First of all, it is illegal for the company to take away benefits you now have in order to punish you for voting for the union.
Secondly, the purpose of a union contract is to protect those benefits, to make sure that the company does not change your pension or your health benefits, or suddenly institute unfair work rules. The company may try to scare you into thinking you will lose your current benefits, but really, they are just worried that you will now have union protection over those benefits.
And let’s be honest, if the company thought that they could get rid of all your benefits and have you work cheaper under a union, don’t you think the company would have invited us here?