No no no no no.

God, no.

Over at /r/badhistory, this would get quite the laughs. That aside, let me help you with this one.

There is already this thread on pretty much the exact same question you just asked. The general consensus is that Lincoln, as reinforced by many of his quotes, never liked slavery. As he said in 1854, in a speech in Peoria:

This declared indifference, but as I must think, covert real zeal for the spread of slavery, I can not but hate. I hate it because of the monstrous injustice of slavery itself. I hate it because it deprives our republican example of its just influence in the world---enables the enemies of free institutions, with plausibility, to taunt us as hypocrites---causes the real friends of freedom to doubt our sincerity, and especially because it forces so many really good men amongst ourselves into an open war with the very fundamental principles of civil liberty---criticising the Declaration of Independence, and insisting that there is no right principle of action but self-interest.

Source: http://www.nps.gov/liho/historyculture/peoriaspeech.htm

Lincoln, from the get-go, makes it very clear he hates slavery. He hated it all along. However, he wasn't planning to abolish it. He made that clear in 1854 in that speech too:

Before proceeding, let me say I think I have no prejudice against the Southern people. They are just what we would be in their situation. If slavery did not now exist amongst them, they would not introduce it. If it did now exist amongst us, we should not instantly give it up.

There are so many source documents that reinforce this point of view, and make clear that he hated slavery, but didn't want to divide the country by trying to abolish it immediately. I can quote more, if you'd like, but I think this should suffice to show he always hated it.

As for emancipation, there's a little bit of context to be made here.

Did ethical and moral concerns influence Lincoln, or did he issue the Emancipation Proclamation only out of wartime expediency?

Yes, definitely, ethical and moral concerns plagued Lincoln about slavery. However, he had a few things on his mind:

1. Alienating the border states by forcing them to give up slavery would've gone against his promise not to push for the abolition of slavery, at least at the start of the war. But this is irrelevant under the other points I'll mention. Just be aware that alienating states was not something Lincoln wanted to do, not during war with the South.

2. The Emancipation Proclamation came in the form it did, in the way it did. It was targeted towards the South, and only the South, for a very simple reason. Lincoln viewed the South as states in rebellion, not as a foreign entity/another country. This is made clear by his suspension of the writ of habeas corpus, which is provided for in the Constitution:

The Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it.

He viewed it, not as an invasion (which is clear, they were seceding, not invading), but as an act of rebellion. Why is this important? Well, consider this: during a rebellion, Lincoln as executive and commander-in-chief can (in a grey legal area) seize the property (ie. slaves) of the South. /u/Georgy_K_Zhukov made this clear in this post, and explained why the Proclamation only applied to the South (at least, in part).

Should the reasons motivating emancipation matter to how we evaluate Lincoln as a leader?

I don't know. That's up to you. Are you a utilitarian, who views that the ends justify the means? If so, then you must think that the removal of slavery was a good thing, and Lincoln was instrumental in it, and therefore the ends were justified and good, therefore Lincoln was good. Are you a deontologist, in that you think the means themselves determine the "goodness" of a person? If so, then you must think Lincoln was good, because he wanted to get rid of slavery without war (over time, basically, but to start by stopping its expansion). Therefore, Lincoln is good.

(That last part is open to interpretation, it was a joke).

Lincoln opposed slavery, but did not think that he (if elected president) had the power (constitutionally) to abolish it. (His election platform was to prevent its spread into new territiories - which he did think he had the constitutional authority to implement).

Both wartime expediency and wartime opportunity led Lincoln to issue the Emancipation Proclamation. He thought it would be useful. He also thought that using his war powers he could emancipate the slaves constitutionally (only in the rebellious states, not in the Union (border) states where slavery was legal).

Lincoln gave the 'reason' for fighting the Civil War, and expressed his views on slavery in his Gettysburg Address:

"Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.

Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure."

Source: http://www.abrahamlincolnonline.org/lincoln/speeches/gettysburg.htm

In this great speech, that genius Abraham Lincoln managed to cover, in a few short words, both reasons for fighting the civil war:

A democratic nation, 'conceived in liberty" cannot 'long endure' if the minority which is outvoted by the majority can just say, "Well, we didn't like that vote. We secede."

Democracy only works if a majority on a constitutional issue is binding. If it is not, democracy will not 'long endure' and anarchy, or some other form of government will replace it.

The United States was "dedicated to the proposition that all men are created equal". Slavery is a denial of that proposition. Lincoln ran on a platform to ban the further spread of slavery into the territories. He didn't think (if elected) that he had the constitutional authority to ban slavery in states where it already existed, but he clearly thought it was incompatible with the essential tenets of the 'New Nation'.

It was, of course his election, bringing with it the promise of banning the spread of slavery, which caused the secession, threatening the concept of Democratic government.

Lincoln, quite eloquently expressed that the Union was fighting for two reasons, to oppose slavery where possible, and to preserve Constitutional Democracy as a form of government.

The war made the abolition of slavery possible (constitutionally) in the rebellious states (at least according to Lincoln's interpretation) and he took the opportunity and acted with the Emancipation declaration.