I think what I'm seeing here is that a lot of the issue is in how the word "lust" is used. The brunt of the responsibility of properly understood communication lies on the speaker, not the receiver. At one time, back when scripture was just beginning to be translated to English, a lot of words like lust had different connotations than they do today. Maybe in the 17th century if someone said "I lust after God" it would be understood without question that the speaker was saying one of his main desires in life is to follow, worship, and love God. Today, the common use of the word has changed somewhat. Today a Christian might hear that statement and immediately understand what it meant, but a worldly non-christian's first picture in his mind when he hears that word will probably be of a sexual nature because in today's society we've given the word a primarily sexual context. The non-christian, or even a new Christian or one who has not had a lot of fellowship with other believers who speak this way, is not as familiar with the particular vernacular used among Christians and won't immediately understand it the way it was meant.
This is why we need to be careful in how we speak to or around non-christians if our goal is to be witnesses to them. Another example is "the flesh". How many times have I heard street preachers or other evangelists speaking primarily to non-christians use that term when they are talking about human earthly desires that are contrary to God. We understand it as a Biblical term because we've immersed ourselves in this rather unique dialect, but remember, the majority of responsibility for the message being understood is on the speaker. Much like with "lust", when the average non-christian in our 21st century American society hears the word "flesh" they think of something sexual and tend to limit their understanding to just that! We need to be careful to make sure we are properly understood. Even though saying "I lust after God" is perfectly acceptable and even commendable, I would not use that term today because I care that the person hearing my message understands it to mean what I actually mean.