Notice that, although you may see a reference to The Muslim Brotherhood here and there, like when you click on the "Islah Party" in the quote of the post below, keep in mind that the Egyptian one could be different and that in many issues it may have its own separate path from those associated with the Saudis or The Muslim Brotherhood of Syria.     

Even before this attack by the Saudis, look at its involvement and the kind of manipulation and control and creation of a system far from providing equality for all as could THIS from Wikipedia suggests:

"In the absence of strong state institutions, elite politics in Yemen constituted a de facto form of collaborative governance, where competing tribal, regional, religious and political interests agreed to hold themselves in check through tacit acceptance of the balance it produced.^[15] The informal political settlement was held together by a power-sharing deal between three men: president Ali Abdullah Saleh, who controlled the state; major general Ali Mohsen al-Ahmar, who controlled the largest share of the army; and sheikh Abdullah al-Ahmar, figurehead of the Islamist Islah party and Saudi Arabia's chosen broker of transnational patronage payments to various political players,^[16] including tribalsheikhs.^{[17][18][19][20]} The Saudi payments have been intended to facilitate the tribes autonomy from the Yemeni government and to give the Saudi government a mechanism with which to weigh in on Yemen's political decision making.^[21]

... Saudi Arabia's main concern was to maintain its influence in Yemen through some old regime figures and other tribal leaders who were part of the so-called "GCC initiative""

Remember, the actions and intentions mentioned here are not related to some democratic country that is also not known for targeting a specific group. On the contrary, this is a report suggesting talking and walking like a duck related to what we already know as a duck. 

And for the guy who describe himself as the legitimate president, HERE is how he was elected according to wikipedia

"A presidential election was held in Yemen on 21 February 2012. Acting President Abd Rabbuh Mansur al-Hadi was the only candidate in the election. He was sworn in as president of Yemen on 25 February 2012 in the Presidential Palace...Hadi won 99.8 percent of the vote."   

Like I said earlier that purpose also needs to be declared to that group because currently the action being taken has the Saudi face on it which clearly does not reflect democracy or justice.

One could also say that there were no signs to support that the group being attacked by the Saudis is a bad enough alternative to make taking control from it with no regard to the kind of system that would replace it a valid purpose.

Also, like I stated previously, there was no showing of crimes and atrocities for the group  being attacked by the Saudis in Yemen that could be used as an argument for its elimination being itself the purpose.   

People here need to ask this president what is that which he wants to do there? What are his objectives and how he intends to reach them? Suppose that those against whom he approves and supports the Saudi attacks are no longer in control of any place, what is the next step in his plan? Would we be the one building a government there or would we also just let that to the Saudis?   

This president may also needs to be told that he cannot attack an entity or stand with and support such attack in order to balance things out because you previously attacked an entity from the opposing side. People are not objects. Every person should be dealt with according to his own actions.