Talmidim of rav shlomo zalman aurbach write that once he and kapach were at a wedding, where kapach was supposed to be a witness, and rav shlomo zalman, the mesader kidushin. Knowing that kapach was pasul l’aidus, but not wanting to cause a scene or offend him needlessly, he said “it’s not befitting your kovod for me to be mesader and you a witness… let’s change places,” since there is no requirement that a mesader kidushin be…. anything.
And yes, as the sonei Torah are quick to point out, rav ovadia yosef writes that kapach is not an apikores. He also had to deal with him on a regular basis. He couldn’t refuse to answer, either. So he wrote something which was dan lekaf zchus; what is he to do if he finds things in kabalah which to him sound like avodah zara? It’s not his fault.
Of course, it’s very much his fault, because he wasn’t living under a rock. He knew full well how many gedolei yisroel – all of them, including in Yemen, had accepted kabalah. Rav ovadia didn’t say that denying them would be acceptable. He found a very expedient way to avoid a very messy machlokes with a person who had zero regard for talmidei chachamim, which would have jeopardized his mission of spreading Torah among a very neglected part of klal yisroel.