An AI is made of material parts, and those parts follow physical laws. The only thing it can do is to follow those laws. The AI’s “goals” will be a description of what it perceives itself to be tending toward according to those laws.

The final sentence seems to me definitely false, especially as an extension of the previous two. Consider:

A human is made of material parts, and those parts follow physical laws. The only thing it can do is to follow those laws. The human's "goals” will be a description of what it perceives itself to be tending toward according to those laws.

Humans are made of material parts following physical law, yet we clearly can and usually do have goals outside, and sometimes in direct contradiction to, our current trends. Do you have some property of AIs-but-not-humans in mind that would make the argument carry in only the first case? I can't think of any.