Well, I'd be more careful with the claim about the Croatian name coming from an Iranian source. While that is quite plausible and even probable, it isn't an established fact the way you put it forward. It is a strong hypothesis but there are still debates going on about it. Furthermore, the only material evidence for it comes in the form of the Tanais Tablets, dated to the late 2nd - early 3d century AD. That's very old, we're talking about the Roman empire times at the ancient Greek city of Tanais in the Don river delta, near modern Rostov-on-Don. The city at the time had a mixed Greek, Gothic and Sarmatian population and was a Greek colony for trading with the east and the Scythians, south between the other Greek Black Sea colonies and the north where from Scandinavians and Slavs were sailing down the river Don with furs, amber and slaves. The most important archeological finds are those tablets and a rather well preserved skeleton. The tablets contain many useful information, but for us additionally interesting are two male names writen in Greek but likely of the Scythian or Alan origin - Horóathos and Horoúathos. That's where the Iranian borrowed name for Croats comes from. Interestingly enough, the found skeleton was analyzed for the DNA with 9 Y-chromosome markers obtained from it. The result came as characteristic for the haplogroup R1a - the most typically Slavic one. At any rate, we do have some concrete evidence for a connection there, but many Europeans were excavating there as well and searching for ancient connections. Thor Heyerdahl for example, in his book 'Jakten på Odin' postulated a controversial idea about the connections between Tanais and ancient Scandinavia. He was basing his idea on the old Norse sagas, but he also conducted some archeological research in the preparation for his book...and whether or not his particular hypothesis was right, the fact remains that the Norse along with the Slavs had been traveling to Tanais. The only question is whether they were ancient Norse as he'd thought, or just the Goths and later vikings.

Otherwise, you're totally right...the idea of the Iranian origin of the Croatian people themselves (not just the name), was debunked in academia immediately as it appeared and the nationalists had attempted to push it in the 90s - in order to separate us from the Slavs, of course. This despite the fact that we speak a Slavic language, have slavic culture, heritage, customs, traditions and largely the genes too. This Iranian thing came up at around the same time when the Gothic origin "theory" appeared as well, and was likewise laughed out of any serious scientific institution.