Lord Capulet was inconsiderate because he did not take Juliet’s feelings about marriage into account.
Although it was common for fathers to make decisions for their families in Juliet’s day, by modern standards we would consider Lord Capulet inconsiderate. We have to remember that things were quite different back then. He was the head of his household, and Juliet was supposed to follow his will. From his standpoint, she was the inconsiderate one.
Nonetheless, you could consider Capulet’s insistence that his daughter, who was only fourteen, marry Paris against her wishes very inconsiderate.
Mistress minion you,
Thank me no thankings, nor proud me no prouds,(155)
But fettle your fine joints 'gainst Thursday next
To go with Paris to Saint Peter's Church,
Or I will drag thee on a hurdle thither. (Act 3, Scene 5)
Even by the standards of his time, Lord Capulet’s actions are considered inconsiderate by Juliet, his wife, and Friar Lawrence. His wife even says to him, "You are too hot." Juliet’s Nurse just figures she should go along with it because she might as well, since she does not have much of a future otherwise. However, his words seem harsh and Juliet is very upset. He continues to say that he will disown her if she does not do what he says.
An you be mine, I'll give you to my friend;(200)
An you be not, hang, beg, starve, die in the streets,
For, by my soul, I'll ne'er acknowledge thee,
Nor what is mine shall never do thee good.
Trust to't. Bethink you. I'll not be forsworn. (Act 3, Scene 5)
Not only does not let her decide who to marry, he threatens to kick her out if she does not. He does not give her an opportunity to explain why she doesn’t want to marry Paris, and doesn’t even give her a month or two. He doesn’t even give her a few weeks! That seems pretty ridiculous, and could not have been common practice under even those circumstances.
Since the wedding to Romeo was a secret, why rush the wedding to Paris? This is the really strange part, and the even more inconsiderate part. It’s almost like he knew what he was doing was wrong, and he was either trying to get it over with before someone could stop him or he was trying to get it done before he changed his mind.