infinitive or -ing verb

Question

Listening to Imagine Dragons song, I've found that one fragment is a bit strange (at least for me), and I don't really think it is grammatically correct. Here we go:

The last thing that I do is bring you down...

Here, I believe, the main part is "The last thing is...". So, won't that be better if we use -ing form of the verb in this case? Like this:

The last thing that I do is bringing you down...

There's a chance both are acceptable, but the question is, which one is more preferable?

I appreciate your help!

Answer 1

The form they use in the lyrics is acceptable, and even preferable to the gerund version in this case. There are many cases of of sentences with a noun phrase like all or the only thing followed by a relative clause involving a subject and just do, and then is + a bare verb. We see it in sentences like:

All I do is win

The only thing I could do was watch

So I believe the lyrics in question are preferable as they are.

Note: If you inverted the sides of the word is, then you would need the gerund absolutely, as in:

Bringing you down is the last thing I do