Ich bin den Plänen gegenüber ablehnend eingestellt. Ich stehe diesen Gedanken ablehnend gegenüber. We would rather say in spoken German (depending on the context of course): Ich lehne diese Pläne ab. The above sentences would rather fit into a written formal context.

The first one would be: Ich bin den Plänen gegenüber ablehnend eingestellt. The second one is correct. But I would say it is not a very common sentence, certainly not everyday life expression, it´s advanced German. You´d read it in a book, a novel maybe, for example. Or a formal letter.