Trump's political opponents have to cherry pick the offer though. The offer "from the Russians" is to show how the Russians have been illegally giving assistance to Hillary. The offer is for hard evidence of that accusation.
The substance of the offer has to be disappeared, because the substance of the offer and the claim that "Russia wants to help Trump" are at odds.
Imagine if there is a parallel offer to Camp Hillary - to produce evidence that Team Trump is buying the services of the GRU to run bots in favor of the Trump campaign. Is Hillary colluding with the Russians if she asks to see the evidence?
How? If the Russians had damaging information on Hillary and want to give it to Trump, how is that at odds with wanting to help Trump?