I think that would depend on their motive for volunteering.
If, Kerry was hoping to build a political portfolio [for which there is evidence]; that he was later going to lie about his exploits there in order to malign other soldiers [Winter Soldiers and his factually challenged Congressional testimony]; and if he exploited the "three Purple Hearts ticket home" criteria [also, for which there is evidence], then, no; he wasn't honorable.
And, it's not slander to say so.
By the way, today marks 1,009 days since
John Kerry promised, on national TV, to sign form SF-180 and release his military records.
Frankly, if John O'Neill says he's dishonorable, that's good enough for me.