Basically to understand the Bahai position, we differentiate between Authentic and inaccurate vs false.
I mean, to Bahais only Bahai writings and the Quran are certainly perfectly preserved.
Thus, if a Hadith is quoted in the Bahai Writings, to Bahais it is a correct Hadith. It does not necessarily mean, it is an exact word to word saying of the Prophet. But it means, at least the Prophet said something like this. Just as for example, when Bahai Writings quote the Bible, it does not mean necessarily it is word for word accurate, but overall it is truth. This is what Abdulbaha wrote about authenticity.
Now, in addition to Hadithes which are quoted in Bahai writings, if a Hadith is confirmed by the Quran (I.e. it is based on the Quran), it would be considered true hadith. However, we don't have such instruction in Bahai faith as how to authenticate a Hadith. Hope this clarifies it.
So, officially speaking, if a Hadith is known to be confirmed with Quran, a Bahai would not say, this is a false Hadith. It is a true Hadith, however it may not have been perfectly preserved as the original words that came out of the mouth of Prophet. On the other hand, Bahais also consider words of Shia Imams as truth, if they are confirmed with the Quran or Bahai writings. So, to Bahais it makes no difference if a Hadith is from Sunni or Shia source.