Clan MacTavish is using ever-more-shady methods of confusing and convincing Thom(p)sons that they are somehow connected to Clan MacTavish. It's the only way they can acquire enough clan members to be viable. We did not choose this fight but Thoms need to at least know the truth.
Let me make a few observations (and I can document mine!)
1. MacTavishes did NOT change their names to Thom(p)son after Culloden. The Dunardry branch of MacTavish was not involved in the affair and had no reason to change their names! The Stratherrick branch was involved at Culloden along with the Frasers....and THEY didn't change their names either.
2. Thom(p)son and MacTavish (as well as MacThomas and 27 other names) mean "Son of Thomas." That does not make them the SAME NAME. Thom(p)son was recognized 300 years earlier than MacTavish's first chief (1997). If anything, that makes MacTavish a cadet of Thom(p)son, the larger and older clan (see Are MacTavish Thomsons?)
3. MacTavish is not listed in the Scottish Parliament Roll of the Clans 1587 - Thom(p)son and MacThomas are.
4. The Chief's surname is that of his clan and a clan has only ONE name. Steven MacTavish is the chief of Clan MacTavish and that is the only name he may claim. There aren't enough MacTavish to build a viable clan, so his father invented the Thom(p)son is MacTavish myth in the 1990s by claiming to Anglicize the English name MacTavish to another English name, Thompson. Steven's continuing to claim Thom(p)son AS MacTavish is shameful. Robin Blair personally told Dugald he was only chief of one name (MacTavish) and that name cannot be added to or adulterated by using "/", "-", "=", "+", or anything else by the laws of Scottish heraldry.
5. MacTavish are in Argyll and Thom(p)sons were predominantly in the West March and around Edinburgh (both were on the borders in earlier years). The distance and topography makes it unreasonable. Also, Thom(p)sons in the Argyll area would have joined one of the might clans and that would be one of the Campbells or similar. There was no Clan MacTavish until it had a recognized chief - Dugald MacTavish in 1997.
6. Steven MacTavish is not the 27th recognized chief in an "unbroken line." While claiming direct descent from Taus Coir, there are 3 missing generations in a row before one that actually has a name - Duncan McTamais CAMPBEL (per History of Clan Campbell). But his son is listed in the MacTavish genealogy as "unknown" so they cannot claim descent! The genealogy is hopelessly flawed. And , Dugald MacTavish was the first matriculated chief of Name and Arms MacTavish and that was in 1997. That makes Steven the 2nd. They are claiming every 'head of household' in their genealogy as if they were matriculated chiefs. NOT the same. They like to claim that Lachlan MacTavish was a chief but he was not. He held personal, not chiefly, arms and no MacTavish prior to him held any. The text of Lachlan's Grant of Arms is on the MacTavish website - very plainly personal arms. If they disappear from there, I have a copy.
7. There are no Thom(p)sons in the MacTavish genealogy, so he also cannot make any claims to Thom(p)sons based on genealogy.