Naturally. If Tan Jee Say of Singaporeans First says that he's not interested in negotiating with the other oppo parties and want to go it alone, I'd say that's arrogant too. Otherwise it's a double standard.
Forget about all this argument on what should be construed as 'arrogance' . In the real world when you got nothing to contribute in a propose business partnership, don't expect to find any interested party to negotiate with you. What has this got to do with others for being arrogant just because they are not interested in your proposition and refuse to negotiate? Likewise tell us what did NSP, SFP or SDP offer to entice or even force WP to the negotiating able? A big ZERO.
It has nothing to do with arrogant but being practical. In fact if WP can compromise on their position so easily, what would voters think if WP represents national interests when they become the govt? Bear in mind middleground voters are watching. If WP thinks they are better off walking their own path, then so be it. If non-WP opposition wants unity there is nothing to stop them from forming their own grand coalition without WP. Just don't pin the blame on WP for their own failure to form one.